I think that insensitive family is everywhere. I don't have much trouble with it, mostly because I do speak my mind. But occasionally one of my skinny cousins will make comments on my weight. But I generally chew them out, so the don't do it to often.
When my nephew died though, my mil told Susan, that she knew what Susan was going through, cause she lost her kids too (in the divorce - big difference from a child dying) and that Susan needed to 'get over it'. I couldn't believe it! I mean Susan was getting a lot of rude and insensitivie comments (the neighbor said "Well, at least you know he's in heaven!" *rolls eyes*), but you'd expect family to care enough about you to be polite about it. I like what Lynn says you should say. That will let them know. And frankly, I bet if next time your mom or mil say something you do say "We're f***ing like animals" that they won't ask again. Maybe you should ask them if they want to watch to make sure you're doing it right.
As to getting them to not talk about it . . .good luck. When I was 6 weeks preggo with Daniel my dr told me that he was dead and to expect a misscarriage any day (Daniel just turned 1 - obviously he was fine). I told everyone I didnt' want to talk about it. I called my mom and told her that I didn't want to talk about it, and asked her to call the rest of my family and tell THEM I don't want to talk about it. The first thing that happens? They all called me up, at my house, to talk about it. "Melinda? We know you don't want to talk about it, but . . ." "well then DON'T!!!" Frankly rude and insensitive people are everywhere.