Why would someone be mean to you but then turn around and copy you?

My boyfriend cousin is always rolling his eye when I talk or saying things under his breath when I'm around. We play games together very rarely I'm mostly just trying to play video games with my boyfriend but he joins. After we play I noticed hed use the skin I was using that you have to buy or a certain camo I used. Stuff he never used before intell after we played. Which isn't a big deal but I dont get why hed come off so rude just to turn around a copy me.
Why would someone be mean to you but then turn around and copy you?
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