Tara Guinness married his stepsister Dolores Maria Agatha Wilhelmine Luise von Fürstenberg, daughter of his father's third wife, but was killed in a car crash.

Her father and stepmother took her to Palm Beach for the winters, where she spent time with Rubio's close friend Truman Capote.

As a girl, she became a passionate artist and studied painting under Oskar Kokoschka, as well as Duncan Grant and Sir William Coldstream.

[9] She married Sheridan Hamilton-Temple-Blackwood, 5th and last Marquess of Dufferin and Ava, her fourth cousin (through their great-grandfather Edward Guinness, 1st Earl of Iveagh), at Westminster Abbey on 21 October 1964.

Princess Margaret was among the 2,000 people in attendance, and Arthur Gore, 9th Earl of Arran, then Viscount Sudley, was the best man.

[6][10] In his will, the marquess bequeathed Clandeboye, the 2,000-acre family estate in Bangor, County Down, Northern Ireland, to his widow.