You and your uncle's grandson are first cousins once removed.
your uncles daughter would be your cousin
There is no relation between you and your grandmother's cousin-in-law's grandson.
Your father's great grandson could be your grandson, or your 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.
Your grandson is your sister's great nephew and she is his great aunt.
You grandson is great great nephew to your uncle. You uncle is great great uncle to your grandson
You grandson is great great nephew to your uncle. You uncle is great great uncle to your grandson
The grandchildren of siblings are second cousins to each other.
Your grandson and your great nephew are second cousins to each other.
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.
Great Uncle.
Second cousin.