' is it normal for me to lust after my own cousin'?

When I was in my pre-teens, my cousin had the best looking butt i had ever seen! nice, round, & mouthwatering! and she always wear tight blue jeans. i got turn on and each time i see her, i always look at that mouthwatering butt! and my penis get hard like a rock.now i'm a man and again each time i see her, i look and check out her butt,again getting a hard penis again.IS THIS NORMAL?