If your father's third cousin is an uncle because his brother or sister has a child, then that child and you are fourth cousins.
If your father's third cousin is an uncle because his wife has a brother or sister who has a child, then that child and you are not related to each other.
Your father's niece is your first cousin, and her daughter is your first cousin, once removed.
Yes.
Your Aunt's niece is you (if you are female), your sister, or your First Cousin.
Your grandfather's niece is a first cousin of one of your parents. Her son is your second cousin.
cousin in law.
2nd cousin or 2nd cousin in law.
Your fathers brothers are your uncles. You are their nephew, or niece.
Your grandfather's great great niece is your second cousin, once removed
it could either be your brother/sister or cousin
Your cousin is your Uncle/Aunt's son/daughter. Your niece is your brother/sister's daughter. So your parent's niece is your cousin.
The relation of the mother;s sister to daughter is niece-aunts.
Your grandfather's niece is a first cousin of one of your parents. Her son is your second cousin.