Another what should I do!

I’m currently the worst player in my COD squad, and I don't know what to do... my brother-in-law invited me to play call duty with him and his two cousins, and I am the worst player. This is very hard for me because I hate losing, and I know we are losing because of me. I’m not a terrible player my KD it’s like 1-2 per game, but The rest of the squad is around 4-5 KD per game. I keep missing big plays to save everyone. And if I’m the last one on my team, they all just asked to restart(ouch). They all don’t have any faith that I’ll be able to buy them back.
Does anyone have tips or tricks to help me become a better college duty player, so I don’t feel so lousy playing in their squad?

FYI- my Brother-in-law is the best on the squad. He will sometimes ask me to play duos, and I always say no... I don't want to ruin his win-loss ratio.