We were actually the ones trying for a change, so it's a bit different than your case. We have 50/50 and the Mom works full time and is in school so they are constantly in day care. We weren't asking for a custody change. We wanted the boys to change to our school system b/c it is one of the best in the state (the one they are in now is one of the worst). And then we offered to care for the boys after school to eliminate child care and allow them to play after school sports (which they have been begging to do). We went to a mediator who agreed that it would be a positive and wrote a report stating so. Mom wouldn't agree only b/c she hates the father so much. Anything he wants is a bad idea in her book. We went to court to have a ruling. We thought for sure they'd make the change. His bottom line ruling was that all other factors were secondary. He said something like by law he is required to above all protect a childs stability (i.e. no changes). So even if they aren't in a great environment with them and they spend all their time with a babysitter, in the states mind change should be prevented at all costs. I was thinking that would hopefully work in your favor for someone who is picking at little things to try and drive a change. This is all assuming children are doing fine in their environment. In our case the boys were doing well in school. So why rock the boat? Our lawyer thinks if they'd been struggling it might have gone differently. Which is why I asked how your step kid was doing. If he/she is struggling maybe she'd have a case I don't know. Don't get scared about the little things she may pull up on you. We had so many on our BM. Financial issues, we proved she'd made falsifications to the court several times, lying to the children, constantly insulting BD to the children (she'd labeled his name as Hitler in their cell phone), on and on. She had some crazy stuff back at us (in particular me) that were just weird. NONE of these mattered. And the judge kind of looked at us like....why are you telling me all this. So...whatever she might try and use I wouldn't worry. The only biggy I've ever heard of is child abuse (which is so hard to prove...not saying you do it, but I guess she could try). I read a post earlier where a woman had an alchoholic BM and they still felt it was better to leave the child with the BM. It's crazy I tell you.