Biscailuz was born in Boyle Heights on March 12, 1883. Sheriff Biscailuz's father, Martin V. Biscailuz, was an attorney of French-Basque descent. His mother, Ida Rose Warren, was a descendant of Spanish pioneer Jose Maria Claudio Lopez, a soldier at the San Gabriel Mission. Her father William Warren was an early Los Angeles city marshal killed in a gun battle in 1870.