unknown tree in the backyard

i got 3 of these growing, all different sizes...







any help would be nice, ive heard everything from apricot to kumquat to avacado, i doubt any of these, any help would be appreciated.

thanks,
~b

haha, definitely not kumquat, definitely not avacado, definitely not apricot (those all have sort of citrus like, or heart shaped smaller leaves). Can only help that much, however; I've never seen anything like that before.