Sounds like a tough situation. I wish I had some easy answer to give you.

Based on what you are saying, it sounds as though your ex is not keeping the well-being of your children as his first priority when they are with him. The only thing I don't know is how often he gets to have your daughters over night.

If you are accurate that they have only been seeing each other for three weeks and are almost living together, that doesn't sound like the basis for a healthy/stable relationship. Sure there is "true love" and all that, but in general this is not a good sign.

What is happening is probably not healthy. The fact that the new girlfriend called your house after three weeks (?and perhaps three visits with your daughters?), is over the top in my mind. There is a small chance there are things being mis-communicated or due to limited contact you are not getting the full picture. Trust your instinct though. If it doesn't feel right, it probably isn't. It doesn't sound like you're being petty and jealous, nor have any reason to. You are thinking of your daughters. Keep that up.

Stay on top of this situation. I don't think what is happening is the basis for any legal challenge in custody arrangements, but if you have other things that trouble you and you think you have a good case and that would be good for you kids, you might consider going that route. Perhaps overnight visits are not appropriate. It is worth a brief talk with a lawyer at the very least and hopefully can be avoided.

Having said all of that, perhaps the two of you could see a counselor/therapist together or mediator. They could help you negotiate some boundaries that you can both agree to. This doesn't sound realistic, but might be worth doing some reasearch into.

I think you are justified in being concerned. You said you're on good terms with his family - what do they think of this? Would an "intervention" type discussion be a possibility? I'm just thinkin' that if nobody confronts him but you, then (in his mind) you are just the bitchy jealous ex. 6 and 8 are still an impressionable age, so if you and his family can't get him to view things in light of what's best for the girls I would definitely go the mediator route. You said he made some pretty crazy rules when you started dating - which ones has he broken so far? Maybe you could make a (written) modified guideline re: dating and how much/what kind of contact would be healthy for the girls. I'm just throwing out ideas... definitely a tough situation.

best of luck!

His being screwed up seems a bigger deal than his live in girlfriend rapidly taking on a step-mommy role. It seems like you could probably talk with him about it -- probably better with his sister there -- and they can be sensitive to your not wanting another woman to say she is your daughter's mommy. My 2 1/2 year old is really clear on who is his real mommy and who is his "step mommy" (actually, some kid in a playground called my gf his step mommy and he has not dropped it, we just call her by her name). It sounds like it should not be hard to diffuse.

Maybe I'm not really understanding the situation all that well but this doesn't seem like grounds for changing the custody arrangement. Hopefully your daughters in the future will end up with a mommy & step daddy they love and a daddy & step mommy they love.

thanks to all who shared, i apreciate it., but it was all hot air as per usual. we finished at court and got our final papers with out one word about it from him.