Actually, his friends forgot but his sisters (who he claims to be close to) remembered and made a point of not getting in touch with him/us because they were annoyed at not being invited to DD's party.
I know it sounds bad that they weren't invited but we'd agreed to keep it small (he's got a big family) and simple (I've got a complicated, divorced family!) and just have a few friends with babies over. This had been explained to them.
DP spent most of the day crying as he was so upset that no one had remembered. He's since forgiven them but I'm still furious.
These sisters are in their 40s/50s and all have kids so they should know better than to throw a strop because they're not invited to a baby party.
I don't really need advice, just feeling really sad about it and like I don't know how to broach the subject with SILs. It makes me feel like I just don't want to have anything to do with them (they were pissing me off before this happened) but I know that's not realistic.
Am I over-reacting or have they behaved disgracefully?