I have a twin brother. I used to get a little upset because whenever I found something I was good at, he'd decide to give it a shot, and without even trying, he'd turn out to be better than me after taking have the time to learn the skill.
The inferiority complex didn't form until three boyfriends (in a row) came out of the closet immediately after dating me. All three of them said the same thing. "I guess I was just more interested in your brother..." My brother's not gay.