Just how much responsibility does a step parent have for their step kids?

I'm no expert in the matter, but IMHO, as far as how much responsibility you should take on is a discussion you should have with your future hubby. I can understand why it feels so overwhelming to take care of children who seem to misbehave and are all riled up, but it really just seems like they're acting out because they're not getting the affection and support they need from a mother, their mother. Children really are very easily influenced by their parents, and if she isn't stepping up to plate and constantly living her life the way it is, it's having a major affect on them.

What you're doing as it is, is good enough. That really is all you can do at this point. I know it costs a lot of money in legal fees to gain complete sole custody, but perhaps the damage in fees would be worth protecting those children's well beings? I would speak to a legal aid for professional advice as to what the best actions to take are.

I'm probably jaded due to a bad marriage, but I'm going to be honest and tell you that bad step-kids can RUIN A MARRIAGE. I know you think I'm awful and mean and horrible, but I'm just being honest.

I know you love the man you're engaged to and all but I would think real long and hard before marrying into this situation. Like I said, I know I sound mean and horrible and like a complete witch, but I am speaking from experience. There's only so much good you can do as a step parent when the actual parents (or in your case parent singular, not plural) are doing a poor job of raising their child. You will be fighting this battle the REST OF YOUR LIFE. It will never go away or get better!

I really do wish you the best and I know you hate my answer, but I felt compelled to be honest. :-)

Legal guardianship is a separate issue

As far as treating them goes - you treat them as your own. Do whats best for them even if you need to sacrifice something. If you dont like the idea, dont marry a man with kids.

There will always be drama with the bio mother. Always. She's there real mother and nothing will change that. If you dont like it, lol dont marry a man with kids!!!!

You are doing what you can with what you've been given. You can't control their circumstances with their mother...unless you do get custody. Until then, you have to do the best you can with them. While they're in your care, try to be as stable and supportive as possible. Teach them what you can. Do for them as if they were your children. Hopefully one day it will all work out and you can afford custody of them.

I believe the cost of custody would outweigh the headache of dealing with them like they are?

you dont have ANY responsibility for them, you arent even their step mother yet and she has no right to think you need to be taking care of her kids. she is their mother and needs to get off her dead @$$ and act like one..on the other hand, if the father decides to take them from her and make you their step parent then you can finish raising them as you see fit, or at least to the extent that he will allow you to. i think its pretty disgusting that she expects you to raise her kids for her.

Yes you are to do more. You are to do what you would do if you gave birth to them. I f you cannot do that then you need to walk away.