They are cousins!!!!!Actually second cousins.
Grandnephew. He became Caesar's adopted son after the assassination.
A grandnephew is the son of your niece or nephew. In other words, if your sibling has a child, and that child has a son, that boy is your grandnephew. The term reflects a generational relationship, indicating a link to your family through your siblings' children.
Your sister's daughter's son would be your grandnephew.
Your niece's son is your great nephew.He would be your grandnephew
Your nephew's son is your great nephew. Your niece's son is also your great nephew.
Your nephew's son is your grand nephew or, some would say, your great nephew. You are his great aunt or great uncle.
Your grandniece is the granddaughter of your brother or sister, and the daughter of your niece or nephew. Your grandnephew is the grandson of your brother or sister, and the son of your niece or nephew.
Your sister's son is your nephew and you are their aunt or uncle. Their baby would be your great nephew. Some use the term grandnephew, but great is more accurate.
Your son would be the uncle of his brother's son.
Your son is your uncle's grandnephew. Your uncle is your son's great uncle.
Your son and your niece are first cousins.
Your Uncle's son is your first cousin.