She was the daughter of Anne "Annie" McKee Armstrong (1864–1925) and William Rhinelander Stewart, Sr. (1852–1929), a wealthy descendant of an old Knickerbocker family.

Anita Rhinelander Stewart was furthermore a descendant, in legitimate lineage,[12] of King James I of Scotland by his wife Joan Beaufort, through their daughter Annabella Gordon, Countess of Huntly.

[6][15] Following her second marriage, she continued to operate a photography studio in Manhattan and spend time at Malbone, their Gothic Revival estate in Newport, Rhode Island.

[23] Her husband was the eldest son of Prince Miguel, Duke of Braganza and Princess Elisabeth of Thurn and Taxis.

[10][28] Anita died at the age of 91, on September 15, 1977 (68 years to the day of her first marriage), at her home in Newport, Rhode Island.