Time to run.  This woman is waving soooo many red flags!  
 

Get out and find someone with whom you. An enjoy your life. 

I married a man with three kids when I was twenty-seven. I was naive, arrogant, and thought because I had had a wonderful stepfather that expanding a family was no big deal. I knew nothing of step dynamics, nor did we do any premarital counseling, and we married after dating only eighteen months. I urge you to learn from my mistakes, and make slowing things down the first step you take. Blending is very complicated, and while I get that you're in that sexy exciting honeymoon period of your relationship, taking a measured, methodical approach is the best way to set things up for success.

You may not realize it, but there were a few big red flags in your post. Firstly, your gf is a very young mother. She started having kids while she was still one herself, so she's learning as she goes and she's made some mistakes. For example, she should not be allowing her kids to call you Dad. Her kids have two parents, you are neither, and it can cause stress and confusion for children as is evidenced in the oldest's behavior. It's also incredibly disrespectful to the actual father. Next, if you've only been dating for a year, that means she introduced you to her kids pretty early, which is not healthy or wise. Thirdly, there's this involved bedtime ritual and the fact that her kids don't listen to her; this is a huge red flag and again, speaks to poor parenting. Children need to learn how to self soothe. They also need structure, rules and consistency, not staying up until midnight. I sense you recognize this is not good policy, and you're already experiencing backlash for not catering to the dysfunction.

One piece of info that would be helpful is, how does your gf support herself and her kids? Is she focused on pursuing education and developing career skills, or is she looking for a man willing to support her? If I were a single young man, I'd be very leery of women with so much baggage. You deserve to have a partner who is your equal and can contribute financially to building a future with you. Having so many kids at such a young age is pretty much choosing to be impoverished. 

Steplife works best when everyone understands what their role is (and is not!) stays in their lane, and maintains an environment where everyone's needs are respected. I suspect you're here because your head is telling you one thing while your hormones are saying something else. Please forget about getting engaged for the time being and just enjoy being the boyfriend as you continue to vet the dynamic. Be extra careful with birth control (countless men have been trapped by an "oops" baby, including my DH) and remember, you're a great catch, while there's lots of single moms out there looking for a meal ticket.

The red flags explained:

Her parenting is subpar and she expects you to to pitch in on all the work as though you're the dad rather than mom's boyfriend. She's being a lazy parent and a bad girlfriend here. You don't even live there, but she gets pissy if you don't clean up after her kids? The entitlement is strong in her, huh?

It's only been a year and you're already talking marriage? Is this idea yours, or is she "hinting" and pressuring you about it? ETA: unstable people like to rush things before their partners find out how deep the crazy goes.

You don't even give a reason for her pursuit of full custody. Is there one? Courts don't like to deviate from 50/50 once it's been established unless something seriously dangerous/neglectful is going on. I would assume you'd mention any of those issues if they were present. You didn't, so I'm going to assume your GF thinks she found a replacement daddy and doesn't need the old one any more. If you have kids with her, she could replace you just as quickly.

Every word you read here is the gospel truth.  At the very LEAST, slow it way down and wear a condom.  Being a step-parent is the hardest thing I've ever done.  I bet if most of us were honest, we would say that if we could go back, we probably wouldn't put ourselves in this situation.

Although most of the posters here are women, if you read around you will find posts from other young men.  Almost all of them have the same scenario as you: incredible, warm, sexy relationship with a young woman they want to marry.  Young children, usually more than one, from a prior relationship.  Poorly parented children, situation with children not improving as the man experiences their behavior on a more frequent basis.  Mother defensive about child discipline.  The young man aware and concerned enough to seek out a step-parent site.

Please read around here and see what you think.  Good luck, you sound like a good guy.

You should not be letting any of the kids call you "dad". You say their dad hates you because he still has feelings for your gf. Whether or not he has feelings for her, she is not his. His children are calling you dad. Whether they do it once a year, once a month, or every day, that's going to make him defensive because they ARE his. You mention he is poisoning them against you, and maybe he is, but in my opinion, allowing them to call you dad is a form of poisoning as well. Of course, I realize it isn't intentional, but I would correct it.

It sounds like there is some confusion between you and your gf that needs to be clarified regarding your role. What do you want your role to be as a member of the family? What does she want your role to be a member of the family? If she expects to clean up after the kids and rub their feet but you're going to feel bitter about it or hold a grudge because you feel obligated, you're going to be irritated and angry for a lot of years. Do you need to be a disciplinarian, or does she handle that? That can be a touchy area, but it's important to determine what the expectations are for both of you. 

Why is she pursuing primary custody? Is that what's best for the kids? How are they going to feel about it, and how will that impact their relationships with you? How will that impact the distaste you already feel toward the kid(s)?

The oldest is at a difficult age, and there is likely more to her feelings than efforts to side with her dad. At 7 years old, she's paying more attention to what's happening. She's more aware of peoples feelings, and if here dad is taking advantage of that, it puts her in a really difficult position. He shouldn't be discussing his feelings about this with any of them. None of them should be put in a position where they are "tattling" on the adults or taking sides. 

I would hold off on the ring. Figure out what's going to happen with custody, have conversations about expectations and boundaries, etc. It's bliss when it's just the two of you, but your struggling with it at 50/50 custody. If she takes primary custody, that just-the-two-of-you time will be even less, and there will likely be some sort of attitude and behavioral issues that will come with it. 

I've been a stepmom for 20 years. What saved us was that DH had my back, whether it was BM being disrespectful or the kids. We struggled with being disrespected, lied to, and alienated for years, but we struggled together, not against each other. It was difficult, frustrating, maddening, and hurtful for both of us, but we had each others backs. We could not have survived it otherwise. My steps were 5 and 8 when I met them. My sd is now 23 and my ss is 27, and I have wonderful loving respectful relationships with both of them. They are old enough now, to understand what they couldn't when they were younger. 

Like you, I did not have children of my own. I don't know if you and your gf would plan to have children together, but if you do, really consider the impact that would create in your family as well. Yours would be different, and you would likely treat them differently which will affect her kids. There's really so much to consider, and with custody up in the air and the feelings you're already having, I hope you'll have honest conversations with your gf about boundaries and expectations before you move forward. Tell her how you feel about being expected to clean up after the kids and rub their feet if it's something you hold a grudge over. Realize that changing custody could very well cause some issues with the kids, as well as with their dad. My profile says I found StepTalk 10 1/2 years ago. It was a blessing to realize that I wasn't the only one feeling like the third wheel in my own home, and struggling to feel relevant and worthy. I hope you find that here too.   

2 people decided to bring them into the world and they can suck it up and do the hard work!!

heck even when hubby invited his sisters or brother over to stay at our marital home when there’s a family wedding nearby and i am busy with my 2 little kids like breastfeeding etc, i do not prioritize feeding them.

if any of them tried dissing me to hubby that i should have made breakfast instead of breastfeeding my kid or catching up on sleep as i was breastfeeding through the night then they can suck it!!

Why does she want primary custody when she already can't handle her kids when they're there only half of the time and how does she plan to finance the court battle?