My best friend is having sex with my twin sister
Ok first off im a guy and me and my friend have been friends for 10 years and hes known my sister for 10 years and they've always kinda disliked each other. When I come home from school I see them making out and I'm like what the heck he leaves really fast and she goes in her room. Later I call my friend and said I thought you to hated each other, he said we used to but then we realized what we have in common, now the two of them are dating and its pretty serious.
I dont know does this mean he finds me atractive or what personally it freaks me the heck out to see them together but I wanted to ask this and end it off saying , is this normal?