I mean let's look at some fact...

Time Spent- 7m
7 Visitors

It's been 10 years that she had to only remember one name. And it's not even a "common name" so you kind of remember it... She's gonna probably ask dad for it.

But after 10 years, if your own sister doesn't know the name of your own kid... Kind of say a lot isn't?
Obviously she's attracted to the entire "sexual" part... Doesn't care of anything else.

She's just like any other guy out there... Primate!
Stay away until she become "Civilized" if one day it happen