His stepmother was Alice Mendias, 'his only source of comfort' when he lived with his father.
By 1949, Trejo shared a room with his cousins at their grandmother's house. After a year, they returned to Los Angeles and Trejo's father turned himself in. Shortly after his birth, Trejo and his family briefly lived in San Antonio, Texas they fled Los Angeles because Dionisio was wanted by police for stabbing another man. He had a maternal half-sister, Dyhan, but saw neither her nor Delores from the age of three and a half until 1965 his father banned his mother from seeing him after Trejo sprained his arm in her care.
His parents met at a dance hall in Highland Park, Los Angeles in 1943. Trejo was the result of an extramarital affair Delores's husband was away fighting in World War II. He is the son of Delores Rivera King and Dionisio 'Dan' Trejo (1922–1981), a construction worker.
Trejo was born on May 16, 1944, on Temple Street in the Echo Park neighborhood of Los Angeles, California, to Mexican-American parents.
