First cousins, as you share a common grandparent.
Your son would be the uncle of his brother's son.
Your son and your niece are first cousins.
Your Uncle's son is your first cousin.
Your nephew's son is your great nephew.
Your nephew.
Well, your cousin's brother is also your cousin, and a cousin's son is also your cousin.
Your sister-in-law's son is your nephew.
Your brother-in-law's son is your nephew
Your son and your aunt's son are first cousins once removed to each other.
Your grandfather's son's son could be:you (if you are a boy)your brotheryour first cousin
daughter-in-law if you're married to jason's son
Great aunty