That would depend on YOUR family history my man..... There is no average when it comes to things like this. What nationality are you? What do your ancestors look like as far as build?
Naturally, it's almost impossible for me to get big arms, because my genetics dictates most of my muscle gain in my core and legs. People often ask me how on earth I can weigh 210 pounds, then I roll up my pant legs and then they understand immediately.