Oliver Platt was born 12 january 1960in Windsor, Ontario, Canada, to American parents Sheila Maynard, a clinical social worker who worked in Islamabad and Nicholas Platt, a career diplomat who served as U.S. ambassador to Pakistan, Zambia, and the Philippines. He has an older brother, Adam Platt, a New York Magazine restaurant critic, and a younger brother, Nicholas Platt Jr. The family moved back to the United States when Platt was three months old. Platt's paternal great-grandfather was artist Charles A. Platt and his maternal great-grandparents were equestrian Arthur Scott Burden (of the industrialist Burden family) and socialite Cynthia Roche. Platt is also a great-great-grandson of diplomat and lawyer Joseph Hodges Choate (through his father) and General Robert Shaw Oliver (through his mother). He is a second cousin once removed of Diana, Princess of Wales, and of her brother Charles Spencer, 9th Earl Spencer, through his great-great-grandparents, MP James Roche and heiress Frances Ellen Work. When asked about Diana, Platt has said, "I never met her. It's a non-story. I'd love to tell you we were confidantes. The truth is I don't know much more about it than you do.

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