He is your second removed uncle. (just uncle is fine)
Your great-cousin.
The child of your father's first cousin is your second cousin
Your first cousin's father is your uncle. Your second cousin's father may be your first cousin once removed, or may not be related to you at all.
You and your father's first cousin are first cousins, once removed.
You would call your father's brother's granddaughter's son your second cousin. In family terms, your father's brother is your uncle, his granddaughter is your cousin, and her son is your second cousin.
The child of you father's first cousin is your second cousin.
Your father's aunt's daughter is your father's first cousin and your first cousin, once removed.
Cousin
Cousin
to you, she is your first cousin. to your father, she is his niece.
Your father's brother's son is your first cousin.
Your father's brother's son is your first cousin.