In almost every family I know, they would be called grandmother. Even though there may not be an actual relationship. In many families, she would be referred to by her first name or as grandfather's wife.
If it's YOUR wife's grand-father - he would be your 'grand-father-in-law' OR you could just call him by his first name.
Your great great grandfather.
Your father's grandfather is your great grandfather.
Your great grandfather
Your great grandfather
Your great great grandfather.
Mother in-law
Sugar Daddy
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.
your father-in-law's house