Your great great grandfather's great great great grandson could be:
and more.
Your great great uncle's great grandson is your third cousin.
The children of siblings are first cousins.
The grandchildren of siblings are second cousins.
The great grandchildren of siblings are third cousins.
Your great great great great grandfathers son is your great great great grandfather, or your first cousin five times removed.
Your great great grandfather's first cousin is your first cousin, thrice removed (i.e. three times removed.)
Your great-great-uncle's son is your first cousin, twice removed.
Your great great grandfather's great great nephew is your parent's third cousin and your third cousin once removed.
Your great great great great grandfather's great great great nephew is your fourth cousin, twice removed.
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