Your great great grandfather.
Your great great grandfather.
Your father's grandfather is your great grandfather.
Your great grandfather
Your great grandfather
Your father's grandfather is your great grandfather.
Your grandfather's brother is your great uncle.
You call him grandfather.
He would be your great, great grandfather, but you could call him whatever endearing name you and he prefer -- Granddad, Papa, Grandpa, etc.
a grandfather*draw out the vowels an roll the r
Your grandfather's brother is your Great Uncle.
The children of your grandfather's brother are your first cousins, once removed. You can also call them by their names.
In Latin (the language) Avus means Grandfather.