You do realize he's the cause of their behavior right? Maybe you need to make him afraid of driving YOU away and insist he parent his kids properly. 

Always nice to welcome a UK member!  I do think tog is right and I'm against bending oneself out of shape to accommodate the bad behaviour of a partner's kids - he needs to realise that they're a pain in the backside a lot of the time and do something about it.   It is totally on him if they're poorly behaved and he needs to parent better.  Having said that - it might be worth checking - if you've never been around kids much, nor are a parent yourself - whether your expectations are reasonable based on their ages. You could try asking friends or relatives with kids of a similar age.   Also be aware that problems with step kids do not stop when they move out! You only need to look at the adult step kids section here.  When someone says they're engaged and they're having step issues, I always recommend a loooooong engagement and don't give up your own accommodation prematurely - you may need a bolt hole. 

Check my 'free advice' post for more detail.  Please be aware that this will NOT change without BF changing.  You are not yet fully committed so hard choice time.  If you really feel he is the one and you truly want to make this work, then I suggest you have very open, direct talks with him one on one, no distractions.  Make sure that you fully understand his feelings and needs and the he fully understands yours. 

Unless the relationship becomes the center that supports you two and the kids then this will be an experiment in misery for you.  If you two are Not on the same page and not a united front this will fail. 

Please also be aware these days moving out near 18 is by no means a sure thing.  Be realistic, I have a 28 year old SS paying rent and living upstairs.

If you don't think you will be able to tolerate these three kids, you should definitely pump the brakes on getting married.

These are 3 kids that are the product of your husband's upbringing.  The genetics.. their behavior.. his parenting.. are all going to impact you.

It sounds that despite being "wonderful".. he isn't a great parent.. his kids reflect that. 

you can't ignore their existence and it will NOT improve with time unless your SO has a serious commitment to improving his kid's behavior.  Even then.. with your distaste in general for kids period.. I just don't think this will be the right circumstance for you.

It's like saying.. "he is just the most perfect match.. except for the fact that he is a serial killer".. some parts of a person's life can't be compartmentalized.

I'd reconsider getting married to this man and having a serious conversation with him about his kids and their behavior. You have to put it out there so at least you give him an opportunity to improve and change the situation. If he doesn't take the necessary measures to fix this, you already know where you stand. It's good that you are realizing this now before investing years into a relationship that is going nowhere.

You have to have a conversation with him about his kids. And you can do that without attacking the kids (although he might hear it otherwise). 

You might not want to lose him, but if he's not willing to accommodate what you need for a happy life, he's really not a very good life partner. And it's better to find out NOW. Otherwise, in a few years, you'll be filled with resentment, disappointed in your marriage, and wonder where the happy you went.

Do read the adult step forum to get a glimpse of your life when kids are raised with lazy or guilty parenting.

I strongly support what KES stated. I wish I would have had a longer engagement instead of just 6 months. We dated for 6 mo and engaged for 6 months. Anyway, take your time. 

I think it comes down to the very simple concept of "if you do not want to be a stepmother.. do not date/marry a many with children". period.  No judgement here.. not everyone wants to have kids or be around them.  

Your BF obviously has kids.. he has kids who haven't been raised very civilized to boot.  He had a hand in that.. and kids are not going away at 18 either.. then they are parasite adults and have grandkids that need to be catered to.  You have a chance to jump off the wagon while it's still going slowly.  I would do it if you don't think this is for you.

Your SO is playing along with SK.  You must also understand that it only one BM accident away of having SK 27/7/365. Or BM fibdimg a boy toy and dumping her kids on you.  If you do not like kids or SK this is not the relationship you you.

I feel your pain. So you can borrow my crystal ball here for a minute. I never wanted kids either. My DH's kids were 17, 13 & 7 when we met. We got married and it's been a rocky road ever since. If you work, you may as well accept that your paycheck is going to those kids. Mine went to clothes, food and all that stuff but it also went to fines, restitutions and lawyers when the 2 boys got old enough to get into legal trouble. So now there are 2 grandbabies. My DH called me granny 2x & grandma 2x the other day when the 10 month old was here. I'm still boiling over that one. When you have SK's, there is NEVER a point where you take a deep breath and say it's finally over. If you consider them a ball and chain now, it will remain that way forever, only the ball will get heavier. I'd like to start a new life somewhere!  My DH's family is no substitute for what I don't have in my life and don't necessarily want. I just have to grin and bear it. When I was younger, my hormones did all the thinking instead of my head. Now my head has taken over rational thought.  : /  It is no wonder I have a treatment-resistant anxiety disorder!

If you don't want to be a SM don't marry a man with prior relationship breeding experiments.

Pretty simple.

And another "adorable" man who has managed to create a herd of "spoiled and entitled" spawn.  smh

What exactly is so adorable about this failed parent of a non man?

You are not driving him away.  He is driving away at all hours of the day and night to cater to his toxic children.

Pull your head out of your butt, take off the rose colored glasses and find a partner that is worth a shit rather than this spawn worshiping failure of a parent, failure of a partner and failure of a man.  He does not make you or the relationship his priority so cut him loose.  No partner will value or prioritize you if you do not prioritize yourself.

Do not get married yet! Long engagement gives you time to deal or choose to leave. Don't let him pressure you on this. If he makes marriage an ultimatum or pushes for it, it might be his way of preventing you from leaving. You WILL resent this if you don't take time to think it over. You need to come first. If he doesn't accept how difficult it is for you and that you need time he isn't the right one.

I'm sorry you're having to go through this. I'm sure you love your fiancee very much. However, everything will probably become way worse after marriage.

You do not have to like your stepkids. You do not have to be their parent. Not even when they are at your house. Your fiance needs to agree to structure and boundaries for when they visit. If he's not willing to do it before the marriage, he will not do it after.

I love my husband very much and life is better now that the kids are out of the house. But I regret ever trying to be a parent to them, even a stepparent. I kind of wish I'd just lived separately, waited for them to grow up and then moved in after they moved out.

Stepmoms have a higher rate of depression than biological mothers. You are not crazy, heartless, or uncaring. You are just recogizing a situation that is not working for you. It's okay to take care of you.

I'm on the other side.  Felt just like you and tied the knot anyway-huge mistake.  Leave now and find peace.  If you don't, you Will separate years down the road when you're too old to be viable.