Can someone be both an ectomorph and a mesomorph?

becuase I think I am an ectomorph, because I am fairly thin, and have a gap between my muscle and my inner elbow, but I have quite a bit of endurance when working out. Also, I have a friend who outweighs me by about 100 pounds, but I can beat him in arm wrestling with ease. Also I have fairly large muscles. but I meet most of the descriptions of an ectomorph.