My family's relationship with my SIL (my brother's wife) has been tricky from the very beginning. We've only ever been nice and welcomed her with open arms but she obviously decided she didn't like us and that was that. She never seems to want to see us but will reluctantly come to some family gatherings, though not all and will have rubbish excuses like she's doing the ironing. She's an only child and has always been very spoilt and is clearly used to getting her own way. She demanded my brother move in with her after 6 months together otherwise their relationship was over, and she has continued to control him and the relationship ever since. They do loads of stuff with her family and friends but when we ask my brother to meet up he always finds an excuse and when I ask my SIL to meet up she flat out ignores my message.
Last year they had their first child and we've got two young children and I really want them to know their cousin. I grew up not knowing my cousins and always thought that was really sad so don't want the same for my children. So we've been making even more of an effort but the relationship seems to have got worse. My SIL has said she is jealous of the relationship my mum has with my children and not with hers, though my mum doesn't often see that grandchild so it's hard to have the same relationship. It's got to a point where SIL is now completely ignoring me and has been avoiding family gatherings so as not to see us. I've messaged her to say it would be nice to chat about any issues and catch up and she's ignored me. I've tried speaking to my brother but he gets extremely defensive and quite nasty towards me.
I don't know what to do next. My mum is of the opinion I should be the bigger person and just accept that's how it is and not say anything about it. She thinks when we do see them at family gatherings I should act normal and like nothing has happened and just be happy with any time we do get to see them. I really struggle with this, it seems very fake and it's upsetting that we can be treated like we are but we just carry on as if it isn't happening. But I do want our children to have a relationship, though that's not happening anyway as any effort to meet up is declined or ignored. Any opinions or advice on where to go next would be appreciated!