Your father's great nephew is the son of your father's niece or nephew.
Your father's nieces and nephews are your first cousins. Their children are your father's great nieces and great nephews, and are your first cousins, once removed.
Your father's great uncle is your great great uncle.
Your nephew's son isyour great nephew. You are his great aunt or great uncle.
You are your great nephew's great aunt if you are a woman, or his great uncle if you are a man.
Your nephew's daughter's son is your great grand nephew (or great great nephew). You are his great great aunt if you are a woman, or his great great uncle if you are a man.
A great uncle is the brother of the great nephew's grandfather or grandmother.
Your nephew's daughter is your great niece. Her son is your great great nephew. You are his great great aunt (if you are a woman) or his great great uncle (if you are a man).
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 nephew's child is your great niece (if a girl) or your great nephew (if a boy).
The children of your grand nephew (or great nephew) are your great great nephews and great great nieces (depending on whether they are girls or boys).
The son of your great niece is your great great nephew.
Your nephew's granddaughter is your great great niece. Depending on whether you are male or female, you are that child's great great uncle or great great aunt.
great nephew
Your sister's daughter is your niece, and her son is your grand nephew (or great nephew). You are his great uncle (if you are a man) or great aunt (if you are a woman).