You and your great uncle's grandson are second cousins.
not to be complicated , but if you have an uncle--> he has a nephew--> as you can see that's not complicated . And if you ask what is a uncles NEPHEW related to an uncles grandfather. in what way ....i would say the nephew is is the great gandfathers great grandson.
Your uncle is your child's great uncle and your grandchild's great great uncle. Your grandson is your uncles great great nephew.
Your grandfather's brother's grandson is your great uncle's grandson. The grandchildren of great aunts and great uncles are your second cousins.
The son of your grandson is your great grandson. You are his great grandmother or great grandfather.
You and your great great aunt's great grandson are third cousins.
Your grandson and your great great niece are second cousins, once removed, to each other
Your daughter and your uncle's great great grandson are second cousins, three times removed.
Your great great great uncle was the brother of one of your great great grandparents. His grandson is the second cousin of your grandparent who is descended from that great great grandparent. Therefore his grandson is your second cousin, twice removed.
Your great-grandmother's first cousin's grandson is your third cousin once removed.
Your aunt's great great great grandson is fourth cousin to one of your parents and therefore your fourth cousin, once removed.
He is Mademe Zeroini's great-great-great-grandson
Your grandson and great grand son could be cousins,(first cousins once removed), they could be uncle and nephew, or they could be father and son. It depends on how they are related to your children. If your great grandson is the grandchild on one of your children and your grandson is the child of a different one of your children, they are first cousins, once removed. If your great grandson is the child of a sibling of your grandson, then they are uncle and nephew. But your great grandson could also be the son of your grandson. Then they are father and son