He is the nephew of novelist Alexander Theroux and writer Peter Theroux. Theroux holds dual British and American citizenship.
His paternal grandmother, Anne Dittami, was an Italian-American grammar school teacher, while his paternal grandfather, Albert Eugène Theroux, was a French-Canadian salesman for the American Leather Oak company. Louis Sebastian Theroux was born in Singapore on, the son of English mother Anne (née Castle) and American travel writer and novelist Paul Theroux.
