Background
She was a granddaughter of Robert Wood Johnson I (co-founder of Johnson & Johnson), and of Bermudian politician, soldier, and lawyer, Colonel Thomas Melville Dill. Johnson was born in New Brunswick, New Jersey. Her father was John Seward Johnson I, and her mother was Ruth Dill, the sister of actress Diana Dill, therefore made her a first cousin of actor Michael Douglas.
Johnson grew up with five siblings: Elaine Johnson, John Seward Johnson II, Diana Melville Johnson, Jennifer Underwood Johnson, and James Loring "Jimmy" Johnson.