My son is 11 next week. I have been divorced since he was 4 and he sees my ex regularly but my husband and I are the 'real' mom and dad.
This kind of struggle is really normal, even with good kids, IMO. But I think you need to look honestly at how YOU feel about things too- in your post, you say
'and they aren't even mine' - but if you are responsible for them, they ARE yours so you need to just get accustomed to that! It sounds like you have a good premise to start from, but if you sort of still feel like his kids 'aren't really yours' - then the kids probably sense that too, and that is NOT going to help you manage them.
I would start by calling a family meeting. First off, you and your husband need to ABSOLUTELY be on the same page at all times or the kids will run rings around you both. Stick together!
You and your husband need to decide ahead of time on some ground rules for ALL the kids- and I don't just mean bedtimes, etc. I mean, what is acceptable and what is not. Not just stuff like 'no talking back' either- really TALK with the kids about what you consider 'talking back' (in our house it is not only WHAT you say, but HOW you say it- if I hear the 'snotty voice' I call my son out on it right away). The kids need to see that you and your husband are a team and won't be played against each other- but they also need to know what their boundaries are!
If you have this meeting and write down very clearly what your expectations are, then no one has the excuse of, "I didn't know" - write down what is unacceptable and what consequence will happen (first back talking= warning, 2nd backtalking= no tv that evening, 3rd backtalking= no sleepover, whatever on the weekend ). You and your husband - and the kids!- can decide what consequences are appropriate, but everyone must understand that is what will happen and YOU must follow through with them.
The kids need to be involved here too- talk to them about what you and your husband do that bothers THEM- you may find things you didn't even realize were an issue, or things that you can compromise on. My advice to you : if you can compromise and just let something go- if it isn't really a big deal to you- LET IT GO. Save your energy for putting out the big fires and step over the small ones! Seriously, you want the kids to be clean, polite and well-behaved and to do their chores and homework and not fight (too much) with each other. Little things- let them go and don't make yourself and the household crazy.
But communication is the key thing. Even if the kids moan and groan about 'another family meeting' keep them up! Encourage everyone to express what they like or are unhappy about.
Last but definitely not least- remember to praise and LOVE A LOT. The stick is no good without the carrot- you can punish and take away privileges, and pretty soon, you have nothing left to take away! Work the angle from BOTH sides and instead of just punishing for not doing chores, include an incentive- " If you put away the dishes and clear the table all week, you can go to see the new 3-d movie with your friends" or " I just want you to know how much I appreciate how big a help you've been all week and how polite you were. I really noticed that you didn't whine or pester me at all at the store. So how about we pick out a new nail polish color and I'll do your nails for you after dinner?" They don't have to be big expensive treats= but always, always acknowledge good behavior and even praise it RIGHT AWAY- just as you want to catch bad behavior right when it happens and say
" Did you hear the way you said that to me? (repeat it in the same voice- they HATE that, lol) That was what you sounded like and it was a really mean voice to use when I only asked you to put away your boots and coat. Why did you say that in such a mean way?"
It is tricky to blend families and everyone is a little uncertain of how far they can go. But family meetings can help- BE a family! It sounds like you have a good attitude about it and I am sure you can work this out! Best of luck to you and your family!