a family having the highest or one of the highest social ranks in a given place.
(often initial capital letters) the family of the president of the U.S. or the family of the governor of a state.
a family descended from a colonist or early settler in a country, region, etc.: one of the first families of Virginia.
Origin of first family
An Americanism dating back to 1835–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for first family
You ain't an old maid; no, nor a Boston first-family widow, neither.Mary-'Gusta|Joseph C. Lincoln