Problem help

Cate

We’re going to this family reunion thing right. So my mom and sister wants to go with us in our car bc there’s room and well we’re going to the same exact place. So my SO is upset bc he doesn’t think it’s fair that my mom hasn’t offered to pitch in for gas. And then another thing. We have to bring drinks but for US only. Like everyone is bringing their own drinks to make it easier on the hosts. And I even went to go buy a dish to take coming from mine and my SO part. He calls me and tells me that he doesn’t think it’s fair that we’re putting everything on him. I don’t get how we are when he’s only responsible for buying mine and his drinks. I already pitched in for the dish coming from both of us. So he’s being such a douche and said that it isn’t fair that my mom isn’t “considerate” to offer atleast $20. My mom has been nothing but nice to him and I hate the fact that he’s saying all this about her and tmmrw will be nice to her face. He even said “i wont even take her money if she offered but I’m mad that she’s not offering” like wtf? What can I tell him? I’m so over it And he’s making a nice trip into a disaster