Your grandson and your brother's grandson are second cousins to each other.
Second cousins.
Your grandson is the great-nephew of your brother.
nothing
a relationship between brothers should be sacred and good....
First cousins
First cousins
Aunt and nephew
grandfather grandson.
Shah Jahan was the grandson of Akbar.
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 father and your aunt are siblings (brother and sister) The grandchildren of siblings are second cousins to each other.
They were brothers.