My sister is dating my boyfriend’s brother😖

When I was first told about it I was honestly mortified. I was really not happy about it at all for days and it caused a fight with my sister who called me unsupportive. I told myself that I would give myself time to open up to it, but it’s been 2 months now and I still feel so weird and uneasy about it. Everyone I talk to about this tells me there’s nothing wrong about them being together as it’s not incest or anything. They say I should just accept it because it’s hurting no one. I know they’re right. I don’t even have anything against them. I guess I just hate the idea of a future where me and my sister’s bf’s might get compared at family functions. Something like “oh your sister and her bf are doing this! Do you guys do that too?” Or “your bf is so much better at doing this than your sisters bf”. It just sounds awkward af. I know it’s bound to happen because my family loves to compare. I also don’t like how it’s made me and my sisters’ arguments overlap with our bf’s. It’s not great when suddenly there’s arguments about which siblings treat each other better. I know I have no right to control their relationship, and I would never tell them what to do, but I can’t stand the idea of seeing pda from them I don’t know why. I feel really confused about how I should move on with this.