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.
its your mothers or fathers cousin (or second cousin)
Your fathers niece is your first cousin.
Your father's niece - would be your cousin.
Your niece or nephew...
Your Aunt's niece is you (if you are female), your sister, or your First Cousin.
Your grandmother's cousin's niece is your parent's second cousin and your second cousin, once removed.
Your great grandmother's niece is your grandparent's first cousin, and your first cousin twice removed.
He is going to be your uncle. And you are his nephew or niece.
Your father's great niece is your first cousin once removed.
Your cousin would either be your father's sibling's child, or your mother's sibling's child. That would make them his niece/nephew.
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.
Your fathers brothers are your uncles. You are their nephew, or niece.
First cousin twice removed.
2nd cousin or 2nd cousin in law.
Your grandfather's great great niece is your second cousin, once removed
Your mother's niece is your first cousin. The son of your first cousin is your first cousin, once removed.
Your father's niece is your first cousin. Her daughter is your "first cousin, once removed".
Your grandfather's niece is a first cousin of one of your parents. Her son is your second cousin.
Your grandfather's niece would be your parent's first cousin. They would be your first cousin once removed. That is because you are one generation away from each other.
There is no actual blood relationship. If this was your mother's niece, it would be your first cousin. In most families, she would be referred to as a cousin, even without the blood connection.
For clarity, lets call your great great grandfather's niece "the niece". The relationship sequence: (1) The niece is the daughter of your great great grandfather's sibling (2) The niece is a 1st cousin of one of your great grandparents (3) The niece is a 1st cousin once removed of one of your grandparents (4) The niece is a 1st cousin twice removed of one of your parents (5) The niece is your 1st cousin three times removed
Your great great grandmother's niece is the daughter of her brother or sibling and thus the first cousin of one of your great grandparents. Therefore, the niece is your first cousin, three times removed
A niece is the daughter of your brother or sister. A cousin is the son or daughter of your parent's sister or brother.
Your niece and your second cousin are second cousins, once removed, to each other - unless they are from different sides of your family. In that case they would not be related at all.
Your grandfather's niece is the first cousin to one of your parents. That would make you first cousins once removed. Most families just use the term cousin.