Your son-in-law's brother's son is not related to you, but is your daughter's nephew.
my brother doesn't have a son.
Your son would be the uncle of his brother's son.
He had three brothers; he was the oldest son.
The son(s) of your parents.
Nephew.
Nephew...
A brother's son is referred to as a nephew.
Great uncle / Great nephew
of course.......................MAIDEN
nephew
his brothers and son and jason
she had a son