Your grandchildren and your nephew are related t each other as first cousins, once removed.
Your uncle's grandchildren are your first cousins, once removed. They and your grand children are your second cousins, once removed
your grand niece or nephew in-law (-Kasadie)
Grand Nephew
Your daughter's daughter is your grand daughter. Your nephew's daughter is the granddaughter of your sibling (your brother or sister) The grandchildren of siblings are second cousins.
Your daughter's daughter is your grand daughter. Your nephew's daughter is the granddaughter of your sibling (your brother or sister) The grandchildren of siblings are second cousins.
Your nephew's first cousin may or may not be related to you, depending on how the cousin is related to your nephew. Your nephew's cousin may be your child, or the child of one of your brothers or sisters. Your nephew is related to you by being the son of your sibling. That sibling has a spouse who may also have borthers and sisters. The children of any of those brothers and sisters are also your nephew's first cousins, but are not related to you.
You are related "by blood" to anyone who is descended from someone you are also descended from. That includes your great grandfather and great grandmother and all their children, grandchildren and great grandchildren.
You are a great great Aunt (or Uncle) to the grandson of your Nephew.
Your nephew's son isyour great nephew. You are his great aunt or great uncle.
The nephew of a wife and the nephew of her husband are not considered to be related to each other. However, both are nephews of the wife and the husband, and the wife and husband are aunt and uncle to both nephews.
Your grandson and your nephew are first cousins, once removed.
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.