Is normal to have a crush on your best friends ex boyfriend?

So I like this guy in my class he is the ex of my bff.He broke up with her in her birthday and the day her cousin past away.I know almost everything about him.We had a dance at my school and me and my best friend started to cry because she still liked him.I was crying because he is pain in the ass but yet I still like him.He always picks on me though. My bff always sees it as flirting.
So is the still normal?