Shikalee
Chibish
I guess people are just confused since Hinata calls him "Big Brother Neji" and stuff. No biggie.
Nii-san doesn't have to be your brother.
It can also be a close friend who you see as a brother.
She respects her cousin so she refers to him as Brother Neji.
yups!
Konohamaru calls Naruto "nii-san" all the time! brothers? I think not!