Two MILs ....oiye lol.
Just try and devided your attention between them as best as you can. Obviously show his mom a tad more attention than his stepmom. I would just try and explain to him that she (stepmom) has never done anything wrong to you personally and you don't think it's right to give her the cold shoulder just because he doesn't particularly like her ~ but that you do understand where he's coming from. That is a tough situation though. I kinda feel at times that I have to choose between my FH and his mom too. He's not as understanding as I am about her condition. He's has alot of hate against the situation because he had to grow up with it. I always try to see both sides in any situation. I tell him that I totally sympathize with him and his dad for having to deal with it all these years. It's not easy to grow up watching your mom act like that. But at the same time, I try to make him understand that his mother didn't ask for this either. When she acts out it's not because she wants to just for the hell of it ~ it's because she just cannot control it. But hey...what can ya do except to be supportive