very curious! I'm not sure how old he is but kids are naturally curious.
We have to be careful around the 10 year old. He learns a ton at his mom's by listening in and we don't want him catching some of the things we say. The 13 year old ss has learned to be incredibly quiet in the room when adults are there chatting and when it might be interesting, hoping that they'll forget he is in the room. He can't remember what he had for dinner last night but he can remember various parts to conversations. It has helped us because apparently bm has been talking with her 21 year old daughter (no dh's) about moving 9 hours away while the 13 yr. old was in the room. He came to us and told us he was worried and that he didn't want to move. We're keeping closer tabs on her comments, etc. now.
Have you asked him why he was listening? You might get a surprisingly true answer that might enlighten you.

Well, if this kid is school-age, he probably already had an idea of what was going on, as children are pretty good at figuring out this sort of stuff (in terms of the problems between mom and dad). If he didn't, than at least Grandma said it (I just read a post about a grandmom that referred to her blood grandchild as a "jew baby", and although terrible in it's own right, older folks can, quite frankly, get away with that stuff). I mean, what's the worst that happen? "Mommy, grandma said something mean about our situation, and nevermind the fact that it's true"? I bet that would sound really sane in court. I wouldn't worry about it too much. I think it is wise to be more careful from now on. And you might have dh sit him down to have a conversation about eavesdropping on adult conversations, and how listening to parts of it can make him misunderstand the context.

Good luck
db

This has got me thinking, now. If he listens in to conversations regarding his mom (and I understand that kids are naturally curious), this could be a sign that he is being grilled for information when he returns home. This is something dh may also want to have a conversation with him about. If this is the case, it's a bigger deal. Children have the right, in my state, and in most states, I believe, to not be poked and prodded about time with other parent when they get back to the first parent. This is a behavior that can, and should be, addressed in court. It often goes along side neurotic behaviors (I don't know if it can be psychologically defined as neurotic, but we all know it is) such as parental alienation, etc. which should also be addressed in court.

Just a thought...actually an afterthought.