the son is to his mother as the nephew is either to his uncle, the mother's sister, or the nephew could be the nephew of the mother's brother.
Your nephew's son is your great nephew and you are his great aunt or great uncle.
Your mother's nephew is your First Cousin.
Mother's grandson as regards her daughter is either her (daughter's) son or her (daughter's) nephew.
The child of your nephew is your great nephew (if a son) or your great niece (if a daughter).
Your nephew and your daughter are first cousins to each other.Your nephew's son and your daughter are first cousins, once removed, to each other.
Your mother's nephew's son is your first cousin once removed.
Your mother's brother is your uncle. Your uncle is your son's great uncle. You are the nephew of your mother's brother. Your son is his great nephew.
You son and your niece are first cousins. Your son and your niece's son are first cousins, once removed.
Your son and your mother's sister are in a "Great Nephew/Great Aunt" relationship.
Your mother's brother's son would be her nephew and your cousin.
Your 2nd cousin. He would be your mother's nephew.
He would be your mother's nephew and your first cousin.
If your wife's nephew is not a son of one of your siblings, there is no relationship between your mom and either your wife's nephew or his son. If your wife's nephew is the son of one of your siblings, then he is your mother's grandchild.
Aunt.
He would be your mother's nephew and your first cousin.
Your son and your mother's sister are in a "Great Nephew/Great Aunt" relationship.
Nephew