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.
Mother's grandson as regards her daughter is either her (daughter's) son or her (daughter's) nephew.
He is your first cousin twice removed.
It does not appear that Thomas Jefferson had any nieces or nephews. He had a daughter, a son in law and two grandsons. He also had an aunt and a first cousin.
Your daughter and your sister's son are first cousins to each other. Your sister's son's daughter (her granddaughter) and your daughter are first cousins, once removed.
Your son and your great nephew (brother's daughter's son) are first cousins, once removed (i.e there is one generation separating them in the family tree) .
Second cousins once removed.
3rd cousin
The sons of your son-in-law's siblings are his nephews. You are not related to them.However, your son-in-law is married to your daughter. The sons of her siblings are also your son-in-law's nephews. They are your grandsons.
Your daughter and your nephew are first cousins. His daughter is your daughter's first cousin, once removed.
You would be his Great Uncle and he would be your Great Nephew.
Your daughter's daughter's son is your great grandson, and you are his great grandfather or great grandmother.
Your brother's son or daughter is your nephew or niece respectively.
You are the great aunt/uncle of your sister's son's daughter, and your sister's son's daughter is your great niece.
Your sister's son and your daughter are first cousins to each other.
Your mother's son is you or your brother. Your mother's son's daughter is your daughter, or your niece. Your mother's son's daughter's mother is your wife, or your sister-in-law.
Your daughter's husband is your son-in-law.
Your nephew's daughter's son is your great-great nephew. Your nephew's daughter is your great niece.