Jean Margaret Wallop was born on 29 April 1935 in
Big Horn,
Wyoming, to The Hon. Oliver Malcolm Wallop (1905–1980) and his wife Jean McGinley Moore (1908–1943). Her paternal grandfather
Oliver Wallop, 8th Earl of Portsmouth, had emigrated to Wyoming and served in the
Wyoming State Legislature before inheriting the British
earldom of Portsmouth. Her maternal great-grandfather was American attorney and financier
William Henry Moore. Wallop had two older brothers, including
Malcolm Wallop,
United States Senator for Wyoming, and one younger sister. Her mother died when she was seven. She was educated at
Garrison Forest School before briefly studying nursing at the
University of Colorado. ==Marriage and issue==