Actually, there are many possibilities. Willie and Noji could not tell him that Willie was Zane. It could be another "uncle", who was good at basketball. It could be that RNasc was right (which is an extremly rare case

) and Willie will be kicked out of the Zanes in the next WiAB update.
I mean, to make a plausible theory, we need solid ground, and Ocean is too greedy to give it in the first season. With him, it could always be this, or it could be that, or it could change altogether in the future. But most likely the uncle means something to the story like the wing earrings.
EDIT: Nika probably just didn't give a shit about his uncle's last name and didn't remember it, just like he didn't remember Vic's last name, even though he read it on her ID.