So I have 3 children me and my 2 sisters have agreed to only buy for each others kids when it comes to birthday & Christmas and not to bother buying for each other. We’ve done this for years now. Last year my oldest sister bought for all the children except 1 of my sons later in the year we argued about this as I thought it was wrong to treat just 1 different. Skip to this year again she never bothered buying for him or even wished him happy birthday but she’s kicked off that her and her children aren’t invited to his birthday party. His birthday party is a week after his birthday it has been kept quiet so she knew nothing about the party and my decision weather to invite them was based on if he received a birthday card this year like his sisters and cousin all have. It’s passed his birthday now and his party is tomorrow and she’s just heard about it of someone in the family yesterday. Up until kicking off about not being invited she’s never once mentioned his birthday. Do I just invite to keep the peace or ignore and move on?