If you're unsure a position of nobility is taken, or if your character would fit in the family tree, don't hesitate to ask an admin
Crownlands:
Regent: Bran I the Broken
Head House: House Stark
Noble Houses:
Westerlands
Warden: Castiel Lannister
Head House: Lannister
Stormlands
Warden:
Head House: Baratheon
The Vale
Warden: Robyn Arryn III
Head House: Arryn
The North
Regent: Sansa Stark
Head House: Stark
Heir: Samuel Stark
The Reach
Warden:
Head House:
Dorne
Warden:
Head House: Martell
Iron Islands
Regent:
Head House: Greyjoy
Riverlands
Warden:
Head House: Tully