Reccomended reading is all the blogs and forums on this site. Going back and searching topics, reading others experiences is the best thing to help you accomplish a few things:

1. Knowing that you are not alone in this journey.

2. Knowing and understanding that you are not wrong or bad in your expectations of:

a. expectations that your Skids bio father should in fact be responsible for his bio children at least financially, for his part.

b. expectations that your Skids should in fact be responsible for chores around the household that you in fact are paying for.

c. expectations that your partner support you in your parenting of skids that live under your roof and are your defacto dependents

d. expectations that your partner get a job and earn wages that will help in supporting the household and her spawn from another dude.

She is gaslighting you in telling you that you need to support her and her spawn as part of some noxious "package".

You are being used.  Sad as it is to realize, she is using you, he spawn are crap and are taking advantage of you and their spineless mother, and her X, as much of a POS as he is, is the smart one.

He knows she and their kids are are a train wreck and is defending himself from them.

So, commit to yourself, rekey the locks, and put them in a refridgerator box under the local overpass where they belong rather than tolerating them to consume your resources, your life, and your happiness.

Your hopefully STBXW is not your equity life partner. She has failed to step up as an adult, a mate, and as a parent. Not your spawn, not your problem.  Not your circus, not your monkeys.

Purge the toxic and get on with living well.  That cannot happen with her or with them in your life.  Living well is the best revenge. Enjoy exacting your revenge.

IMHO of course.

No you're not wrong for any of it. She needs to help out. It's not your responsibility. She needs to parent her kids. They are not your responsibility. And yes, I would be bitter and want out of the marriage too. 

I am not sure where she got the idea that you had to provide for everyone while she does not contribute. I'm also not sure where she got the idea that kids should not be made to do chores around the house or help out. What is she bringing to the table? 

What are the plans for the 20 and 18 year old? At that age, after HS it should be either part-time school/part-time work, full-time school or full-time work with contributing rent and a plan to move out. I hope they aren't sitting around spinning their wheels. 

And all 3 should be contributing a bit to helping out around the house with chores. Who does she think is going to do it for them when she's not there? 

So no you're not wrong. About any of it. And everyone here is pretty much going to say the same thing. 

If it were me. I would lay some boundaries down. 1. She needs a job. 2. They need to help out. And 3. There needs to be a launch plan laid out (it's up to you how long you're willing to put up with the adults living in your house). Is she going to throw a fit? Probably. But you're not being unreasonable. You're simply stating what you will/will not put up with. By age 20, I was ready for my SD to gtfo. It's not easy when they aren't your own kids. Their presence wears on you unfortunately and I was ready to walk out in the marriage because I didn't want a third adult living with me for the next 5 years.
 

A parent’s primary responsibility is raising their children to be mature, conscientious, productive adults and your wife is failing miserably. From what you’ve written about the boys’ biological father, he is equally at fault; a deadbeat dad who neglects to support his own issue.

As you’ve already discovered, when you marry a woman, you also marry her children. Was your relationship a matter of, ‘bait and switch?’ Did you have any idea that you were saddling yourself with a bride who was unwilling to work and, worse still, demanded that you also provide for her and her skiver ex-husband’s spawn? The two of them have a good thing going! 

When I married my husband, his children were teens and my own daughters were attending university. I did not expect him to provide for my children nor did he ask for a cent from me. Our children were our own responsibility!

When my stepchildren misbehaved or were disrespectful, my husband took immediate action. In fact, when his daughter became insufferable, he banned her from our home until she decided to improve her attitude. Doing so was devastating to him but he was totally committed to our marriage. That’s the way it should be! 

My good man, you don’t need folks on StepTalk to advise you that you are being used and abused; it should be clear to anyone with a pulse. Trust me on this, undisciplined children, particularly teens, do not magically improve their conduct without strict guidelines and consistent, uncompromising parenting. Your wife is convinced that her way is the right way, resulting in your being made a fool of in your own home!

The only manner in which I can envision your marriage being saved is for you and your wife to attend sessions with a marriage counsellor experienced in step-family dynamics. Perhaps a neutral third party will be able to open your wife’s eyes to the outrageous imbalance in your household. Otherwise, I’d recommend that you consult the best divorce lawyer in your area and get the hell out of that mess!

I'm 79-years-old and can guarantee you that, at 52, you have a lot of life left to live, There is no need to spend  those years in a miserable situation. Take action! 

The 2 older ones can be responsible for themselves if they won't be an asset to the home. It sounds like all 3 of them are loafing and taking advantage. Even the 13-year-old needs to be doing his own dishes and laundry, and a few more chores. Do the 18 and 20-year-old work, or are they actively working toward further degrees (not dropping basket weaving classes?) Since you are the breadwinner, what you say goes. If your wife doesn't like it, she can get a job and potentially move out. You have the advantage here. These people need to help out or move out. All of them. 

In explaining to her EX about supporting HIS. Kids.  Being 16 months behind in CS.  DW either gets a job or gets her Ex to pay support. Not your monkey not your circus.  She and her EX takes care of her kids. Not you.  This is a bad road to go down.  This attitude could be the real sin behind her divorce 

1.  You are being used.  She should be financially supporting herself and her children.

2.  Her boys are NOT your responsibility.  they have two parents.. they should be supporting them.

3.  You are not wrong for wanting to leave.  And it sounds like you should leave.. I would get legal counsel though.. you may, unfortunately.. end up paying her some spousal support since you have been footing all her bills for 3 years.