The daughter could be considered your cousin through marriage.
The neice of your uncle's new wife is not related to you because you have no shared ancestors, although, if you like her, you may call her your cousin.
not really
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 dad is uncle to your cousin, and your cousin is niece or nephew to your dad..
Your mother's brother is your uncle. Your uncle's daughter is your first cousin. Any child of your first cousin is your first cousin, once removed.
My uncle's niece and I are very good friends. We grew up together and we enjoyed the summers swinging on a rope above the creek.
Your mother's niece is your first cousin. Your first cousin's daughter is your first cousin, once removed.
You are either her aunt or uncle depending upon your gender, and she is your niece.
You son and your niece are first cousins. Your son and your niece's son are first cousins, once removed.
Your uncle's sister could be your mother. Then her niece is your first cousin. Your uncles' sister could be a sister of either your mother or your father, and thus your aunt. Then her niece could be you (if you are a girl), your sister, or one of your first cousins. If your uncle is your uncle because he is married to the sister of you father or your mother, then his sister is not related to you, and neither is her niece, unless the niece is the daughter of that uncle with the sister of one of your parents. Then the niece wold be your first cousin.
Your father's niece is your first cousin, and her daughter is your first cousin, once removed.
If your father is someone's uncle, then that person is your first cousin.
To your uncle, you are his niece or nephew.
Your Dad's niece is your first cousin. Their child would be your first cousin once removed.