Nana's last name is Williams and MC's is Miller. Or the other way around. Either way there is no one named Walker.
I go to the relationship menu, and I get this:
I go to the mod menu, and erase Walker, and it changes to Williams. I have no idea where Walker came from. I have been playing this game since .04 (I think, it was a long time ago now) was first released, I've used Koga's mod this whole time, and I don't remember changing that family name. I did for my MC, but not for Nana and her girls.
But it doesn't matter really. You know who I'm talking about for my comment.