1
Your sister's son is your nephew. Your uncle is your nephew's grand uncle or great uncle.
Your uncle's first cousin is also your parent's first cousin, and your first cousin, once removed - if your uncle is the brother of one of your parents. Sometimes your uncle is the husband of your parent's sister. Then his cousin in not related to you.
Your uncle's first cousin may also be the first cousin of one of your parents if descended fromyour great grandparent. In that case, your uncle's first cousin would be your first cousin, once removed. On the other hand, your uncle's first cousin may be related to that parent of your uncle who is not descended from you great grandparent. In that case, your uncle's first cousin is not related to you.
You can call him Cousin instead of uncle.
Since the cousin is from your half uncle's wife's side of the family the cousin would not be your cousin.
Your uncle's first cousin is also your parent's first cousin, and your first cousin, once removed - if your uncle is the brother of one of your parents. Sometimes your uncle is the husband of your parent's sister. Then his cousin in not related to you.
No. Your uncle is your mother's (or your father's) brother.Your mother's first cousin is your first cousin, once removed.
Your uncle's brother's cousin is also your uncle's cousin. And the cousin's sister is also his cousin. So the question is the same as "Who is your uncle's cousin?" If your uncle is the brother of one of your parents, then his first cousin is your first cousin, once removed. Similarly, his second cousin is your second cousin, once removed, and so forth. If your uncle is the husband of the sister of one of your parents, then his cousin is not related to you.
Your great uncle's granddaughter is your second cousin.
Your great uncle's grandchild is your second cousin. (Your great uncle's child is your first cousin, once removed and your parent's first cousin.)
Your son is your uncle's grandnephew. Your uncle is your son's great uncle.
She'd be your second cousin; your uncle's daughter would be your first cousin.