Is it normal that my brother gets erect when seeing me naked?

My little 12 year old cousin gets his dick hard when he sees me in shorts because when I sit down he sees my legs and he says that he thinks about the smell in my butt and it makes him horny and when he sees my butt he really has a hard dick I decided to let him do what he wanted one time and he pulled my shorts down and my panties down and he smelled my naked butt and he jerk off and he cummed in seconds because my butt stinks and he loved it and it smelled like he wanted it to I put my butt on him now and he get a hard dick fast