Abigail Quincy Adams is a relative of The Addams Family.
She is Gomez Addams' cousin by marriage.
Abigail and the rest of "those Boston one-'d' Adamses" wanted to have Gomez removed as the head of the Family fortune, but eventually dropped those plans. Her grandchildren live in the same city as The Addams Family. Morticia wouldn't dream of having her in the house.
The Addams Family original series episode: