genesister
Your real, genuine, full-blooded sister. Normally, such a title is irrelevant, unless you are introducing someone to your sister-in-law, half sister, step sister, bridge sister, side-step sister, and/or skip sister.
TOM: And this is my genesister Gwendolyn.
ANDREA: Wow! This is your REAL sister?
TOM: Yep!
ANDREA: Wow! This is your REAL sister?
TOM: Yep!