Tobias Vincent Maguire was born in Santa Monica, California, on June 27, 1975, the son of Wendy (née Brown), a secretary turned screenwriter and film producer, and Vincent Maguire, a construction worker and cook. He has four half-brothers. He is of one eighth Austrian and one eighth Puerto Rican descent. His parents, 18 and 20 years old, were unmarried at the time of his birth; the two married and subsequently divorced when Maguire was two. Maguire spent much of his childhood moving from town to town, living with each parent and other family members.