A big brother. Huey's always been (somewhat of) one to Dewey and Louie, and he never thought about wanting one himself... until he met Fenton.

  Basically, what I mean here is that I believe in Huey seeing Fenton like the older brother he never knew he wanted. I decided not to go with "dad" because a) that title would already go to Uncle Donald, and b) I think Fenton might be old enough to be Huey's (surrogate) older brother.

  I also believe in Fenton seeing Huey as "the sweet, supportive little brother I always wished I could have, but then that explosion in my father's lab happened, and..."

  (I'm also thinking that Fenton's middle name would be Alejandro, and Huey would have two middle names: Emmett and Apollo)