That was an instant divorce move IMHO.  Fortunately, you did not marry this POS non man, failed adult, failed partner, and failed father.

Respect yourself and commit to living YOUR best life. That is what we each owe ourselves.  That cannot happen while you wallow around in your SO's shallow and polluted gene pool as he caters to his X and coddles their noxious failed family spawn.

Not only did he abandon you at Christmas, he has repeatedly done it since. As behaviors are the best predictor of performance, I would bet every Cent I have that he did it before Christmas as well.  Any number of times.

He, his X, and their noxious spawn treat you like shit that they just scrape off of their collective shoe anytime they feel like it. Know this. It is that entire shallow and polluted gene pool that is shit.  Time for zero tolerance, call the locksmith to re-key the locks when he leaves to return his spawn to mommy.  He can know when he returns that  you are done.  This only works out if you continue to sacrifice yourself on the altar of SParental martyrdom to this dumbass, his X and their rotten crotch product.

Stop that.  You owe yourself and your DD to live your best life.  Living well is also the best revenge and IMHO you should relish in living that revenge. Write him/them off completely, and get on with living your best life.

If you need more clarity.  This is a 15yo not a 5yo. A 15yo who is dropping her skivies to shake tail at daddy.  These are some serious incestuous desires vibes.  At the very least he has admitted to emotional incest.  Get yourself and your own DD out of this mess. NOW!

Take care of you.

Abandoned you for Christmas? That would have been his "goodbye" from me. 
 

Seriously, get yourself a good counselor. You need an impartial  person  to clearly show you what you are mixed up in. It's not good and it will not end well for you if you continue with this man. He needs to live alone with the mini-wife he's created. 
 

Count yourself fortunate. At 17, her role has been defined and she won't budge from it. So, don't walk away. RUN!!! If you stay, be prepared for a life of troubles all at her hands. And your SO. 

The ''''honeymoon ''''.   Hate to see this relationship in a few years.  SD is ''''controlding''' your SO and yours life.  She saids  jump you say how high.  You already are not happy, in this relationship.  Where do you think it's going from here.  These kids don't  go away at 18.  They keep this happy family not including you for there life time.

Time to move on, you see that

Nothing good can come from this. 

Run

What you SEEEEEE, is what you have. 

It is that simple. 

Make a plan, keep that plan to yourself and move on.

This doesn't magically get any better and will in fact get worse. 

My DH chased his daughter like she was a girlfriend too. Not to the extent that yours does though. She would give him orders and he would comply--nearly every aspect of life from trying a new recipe to buying a birthday gift for his sister. She controlled all. I became invisible when they were in the room together. Everything SD did was always the best, the most amazing. It got old.

Took several meltdowns on my part, then a final "choose your full time wife" ultimatum because I wasn't going to sit on the sidelines any longer while he chased her attention and worshipped her.

The more he included me, and the more she didn't get her way, the angrier she got to the point of convincing herself that HE was the selfish one and she had been mistreated her whole life. She didn't talk to him for about three years, and communication is still rare. My life is peaceful. He can have a relationship with her--I encourage it. But if neither of them put any energy into it, oh well. Not my problem to solve.

Suggest you live your life. If he cancels plans with you to chase after her, you go ahead with the plans anyway with a friend or by yourself. SD doesn't control you. It will take the fear of losing you for him to make any changes, and even then he might not.

Im sorry you're in this club. It's not a fun one. 

I have had similar experiences with a very jealous, angry SS who tries to be DH's mini-wife. He has said of himself at 15 yo that he is a "dady's boy" which prompted his friends to laugh at him, so he never said that again. He has tried everything to exclude me, disrespect me, be in charge, and replace me as the other half of the partnership. I held a lot of resentment, but I kept it to myself because I thought I would be the evil stepmom if I objected. Dh believed that too because I think like many people in society, kids are always the innocent party no matter what toxicity they interject into the family system.

But I've been a lot more vocal in the last half year or so, which has made me less stressed and my dh more stressed. I'm off-loading the anger and stress to the people they belong to. I'm not going to be the one to suffer for everyone's dysfunctions anymore.

I've been reading a book about healthy "primary relationships" (marriage or any long term romantic relationships), and it has really put words to what I can expect and how I've been feeling. Just a few thoughts: The couple should NEVER allow "thirds" (children, exes, addictions, friends, etc. etc.) to get in the way of the primary relationship. According to the author, Stan Tatkin, the #1 job of the bio parent in a blended family is to protect the stepmom "from all corners, particularly from angry children, angry exes and others that would seek to split the new partnership and target the new kid in town. The stepparent is an easy target for all those who resent the changes in the family structure." Mismanaging thirds is "one of the most insidious causes leading to the demise of all adult primary attachment relationships."

Another quote: "Mismanagement of thirds is in the top tier of threatening behaviors that plagues romatic partnerships." It is no joke. If the husband can't manage the children well, there is hardly anything more destabilizing. The problem is that bioparents usually have so many blindspots, guilt, etc. that they cannot hold their kids accountable for their part. They allow kids to insert a win or lose dichotomy, and they usually win. I'm learning that by standing up for myself, there can be a win-win - but the stepmom has to be the queen bee. If she is treated anything less than "top dog" the reaction is never neutral, it is always experienced with humiliation to be robbed of one's rightful place.

I hope this helps. I'm feeling anxious about my own situation, so I might have come off too strong. But I want to encourage you to stand up for yourself. I held back for 6 years thinking that I should be more understanding, and I regret that. Once I started pushing back, dh was upset, but his eyes are starting to open. Good luck.

Someone you enjoy spending time with that is a friend on the spot when the SO goes chasing their failed family progency when canceling plans with you.

Don't ever cancel your own plans. Go, meet new people, invite the work spouse, a close friend, a casual acquantence, a neighbor, etc.  That way the seed is planted in the pea sized brain of the failed family spawn chasing SO that their absence is insiginificant to you enjoying your life.  

Of course it would be ideal for the SO to engage meaningfully. However, never let them destroy your bliss.  Have fun with or without them, and more importantly, in spite of their idiot choices.

At some point they will figure out that they are making themselves insignificant, or you will figure out that they are insignificant, and changes will be made.

Never sacrifice living your best life.  Everyone owes living well to themselves regardless of what circulates around that truth.

IMHO of course.

Well.. that's why we date people for a really long time. .they may eventually show us the kind of person they are.

do you want this dysfunction in your life.. it's a yes or no question... I don't think there will be any real way to "fix" this.. so if your answer is "no".. then.. you know you have reached the end of this relationship.

If you can deal with the drama.. you can stay and disengage.. but you know what you are getting into at this point.

I have a mini-wife on steroids (35). I've been in the fame with DH for almost 30 years. Starting out and probably the first 20 or more years I had extremely low self esteem from being raised by a narcissistic sociopathic father who chose everyone else over me. Through intensive therapy I discovered I was repeating the pattern in my marriage to a man who was obsessed with his mini-wife. I had tried everything under the sun to get my DH to realize what he was doing and how it impacted me and how much agony I was in. What I hadn't done though, was leave or even threaten to. Until...

Something happened where I got in touch with my self worth. I had one foot out the door and was actually creating an exit plan, so why not try one last thing: an epic nuclear melt-down. I let DH have it. Pulled no punches. Used very harsh blunt wording about how I "will be treated like Queen Shit of Turd Island before the sun sets today," and "you need to remember which one of us you're f*cking." Oh yeah, I went there. I even told DH that if he went to SD and said that he's only with me for sex I was convinced that she would have sex with him if it meant having him all to herself. I won't go on with everything else I said or my response will be novel-length but I threw everything at DH about him and his "very sick mini-wife." Yep, I said that. Also mentioned how she's "extremely, extremely, extremely (insert about 10 more extremelies in here) arrogant and that in all of my years working with the crimnally insane, I have never seen anyone more arrogant. Oh yeah. I was quite ashamed of how nutso I was but on the other hand I felt so cleansed after.

I share a bio DDstb25 with DH and I didn't want her to repeat the pattern with her future relationships, so I decided that I would leave and have the epic meltdown on my way out. Only the epic meltdown worked. It's been ten years and there were a couple of slip-ups but a slight reminder and DH rights himself immediately. However, there have been no slip-ups for several years now, so it's all good. I still have a ton of resentment though. I'm not sure that'll ever go away. Not a day goes by that I don't regret marrying a man with brats, one of which is an enmeshed insane mini-wife. Even though DH and I have a completely different marriage, I'm well aware that I should have left anyway because of the resentment that has never really gone away. I even have a secret account and have an escape plan in the event that I decide to leave and spend my golden years in peace. It's a relocation plan and I would relocate so I wouldn't have to worry about running into SD anywhere and seeing her damn face again.

So, even if you have an epic nuclear meltdown if you're amendable to that, and even if it works, there would stll be a ton of resentment and it would take a very long time to not have that hair-trigger worrying response in the event that your SO falls for your SD's tactics. And believe me she will ramp it right up to get your SO back into her clutches.

Also, the root cause of the mini-wife crap is a deep issue within the father. For years just when there was even a slight sign of evolvement in SD or the relationship, DH would sabotage it to knock things back into status quo. After a ton of marital therapy, it came up that DH "just couldn't afford to heal." Reason being that he might lose SD to BM and never see her again. I feel that I'm in a rare case where my DH chose me over his fear of losing SD. That's not the norm with mini-wife dads. They have something within them that drives their enabling of the mini-wife dynamic. It's usually intense fear or guilt. 

I would suggest to you to put your DD first and not let her have your relationship as a model or she'll be repeating that dynamic in her relationships. If you don't want that agony on your DD, then take her and go.

Good luck!

And leaving you at the drop of a hat at Christmas (that must have been so lonely!) and on your date night which you already modify to suit his sorry a$$...  If this is the earlier stages of the relationship, the honeymoon, what's it going to be five years down the line???

It keeps things direct and focused on what they do regardless of why they do it and does not waste time, effort, or emotion on why they are what they are..

Not once during my divorce did I ever give a thought to why my then STBXW was a seriously adulterous whore. That she was made her a write off.  I did invest a ton of effort in engaging a couples therapist and trying to fix things.  Though fixing her was never a consideration. Fixing the marriage was my intent. I did not know during the 5mos of couples therapy that she was cheating. When she walked out of the last couples session  after 5mos of weekly sessions proclaiming that she did not have a problem with sex, the incredible therapist and I gave each other a knowing look. From that point, it was about me and figuring out how to get back to being the man I liked being and living the life I liked living. It had nothing to do with her at that point.

5mos later when we left the courthouse following our final divorce hearing I held the door for her,.  Then as we got to the road I stepped off of the curb, walked across the street, got in my vehicle, and drove off. The last sight of her I ever had was as I drove away I checked my side and rear view mirrors as one does when driving. She was standing on the curb sobbing. I felt nothing. Which made a major impression on me. Usually I am a caring person and do not want anyone upset.  At that point realized how freeing not giving a shit about those who are not additive to my life is.  I never saw her again.  As I stepped off the curb she had reached out and put her hand on my shoulder. I ignored it and stepped into my new life adventure. When I stepped off of the curb she broke into sobs.  She was a nasty biotch in the hearing to the point that the Judge ripped her a new asshole.  

Even with the divorce final, nothing about her changed.  Though I never layed eyes on her again she was like a bad case of jock itch that kept calling.  One call to cry and looking for emotional support. The next a nasty attack in response to some perceived slight.  This cycled for about the next 3yrs.

IMHO, never waste time or effort worrying about why nasty people are nasty. That they are nasty is really all that matters other than scraping their shit lives off of our shoe which is what we owe ourselves.

This may be a selfish position.  It likely is. However, we must defend ourselves from what they do and who they are. Why they do what they do or are that way really is irrelevant.

IMHO of course.