Why am I the only one in my family who has an accent?

Okay, well I have a british accent. Well, it's more of a british texan accent(I live in Texas). I am the only one in my family who has it, my friends hear it in me, people that I just meet hear it, and they don't hear it in my family. I don't know anyone who has a british accent, so I couldn't have picked it up from somebody. And I do have a little british in my blood, also. And I'm 13 btw....if it matters....