He is you grandfather in law
Your great grandfather!
He would be your paternal great grandfather
Yes, the father of your father is your "Paternal Grandfather".
auntie
Your father's father is your grand father and your grandfather's father is your great grandfather.
grandfather comes to mind
Some one in your family in your fathers family, like you great grandfather
Your grandfather's brother's daughter is your first cousin, once removed.
Your great grandfather's nephew was your grandfather's first cousin. You are two generations removed from your grandfather and his cousin. Therefore you and your great grandfather's nephew are first cousins, twice removed.
Your grandfather's great great niece is your second cousin, once removed
Great Uncle.