Your father's father is your grandfather.
He would be the father-in-law.
He would be the father-in-law.
You would call her your stepmother.
You would call your father's sister's husband your uncle-in-law.
Farfar or morfar, it depends on the side of the family. If it was my mothers father then I would call him morfar but if it was my dads father then I would call him farfar.
Just call him by his regular name. It is know different from any other person. He just happened to be the kid of the mother/father your mother/father would be marrying.
Most would call it "unresolved issues with your father".
Most would call it "unresolved issues with your father".
Since your aunt is sister to your mother or father. Your aunt's dad is your mother or father's dad. You would call him your grandfather. Your aunt may also be the wife of your parent's brother. In that case, you are not related to her father.
Your father's brother is your uncle; you are his niece (if you are a girl) or his nephew (if you are a boy).
He would be your cousin, or your father's nephew.
You would call your wife's sister your sister-in-law. If your wife would have a brother he would be your brother-in-law. It is the same thing for a husband's siblings. Your wife's mother would be your mother-in-law. Her father would be father-in-law.