what do we know about derek's sisters??

well, from what i can tell
derek has 4 sisters

amelia (private practice)
- neurologist
Nancy( greys season 3 episode 6)
-OB gyn
Kathleen (mention also in season 3 episode 6)
- psychologist
last one unknown..

is this all we know.. cos i was thinking of composição literária a fã fiction story about them.. and just wanted to be sure if what i know is right of if i'm missing anything.