Your daughter and your uncle's great great grandson are second cousins, three times 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.
If your daughter-in-law's grandson is a child from a marriage before she married your son, or after their marriage ended, her grandson is not related to you. If he is a child of the marriage between your son and your daughter-in-law, then he is your 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 grandmother's sister is your great aunt. Her son's daughter's son is her great grandson. You and your great aunt's great grandson are second cousins, once removed.
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 father's grandfather is your great grandfather. Your great grandfather's daughter could be your father's aunt and your great aunt. The grandson of your great aunt is your second cousin. However, your great grandfather's daughter could also be your father's mother and your grandmother. Then you, one of your brothers, or one of your first cousins, is the grandson in question.
Your grandchild through one daughter and your great grandchild through another daughter are second cousins, once removed.
Your great, great great grandson.
Your daughter's daughter is your grand daughter. Your sister's son's daughter's son is your sister's great grandson and your great great nephew. Your granddaughter and your great great nephew are second cousins, once removed ,to each other.
Your daughter's daughter's son is your great grandson, and you are his great grandfather or great grandmother.
The son of your grandson is your great grandson. You are his great grandmother or great grandfather.
Your great grandmother's brother is your great great uncle. Your parent and the grandson of your great great uncle are Second Cousins. Therefore you and the grandson of your great great uncle are Second Cousins, once removed.