Attracted to someone 6 years younger than me. Help.?

I have never really had many sexual thoughts about men. I am now 21 and I still am not attracted to manly men. When I was young I was abused sexually by my uncle and by other sources. I have such an aversion to beards and masculinity. Its hard for me to find guys my age i like. My only two relationships were with guys my age that looked at least 16. now i have become very chemically attracted to my friend's younger brother. I never act on it. He grabs me, and does things to me and I react like i think its not appropriate, but inside i kind of like it and it bothers me. He is about 6' tall and 150 pounds. He has obviously went through puberty and looks about 16. But he flirts with me and pays attention to me. I cannot understand why I am attracted to him. And him touching me all the time inappropriately doesnt help my case. Im not a sicko, and i would never be attracted to a prepubescent child. I think maybe I have ephebophilic tendencies. not to be confused with pedophilic, which is not what I am. Why is this happening? Why am I attracted to him despite his age?