Leo Najo was born "Leonardo Alaniz" on February 17, 1899 in the small town of La Lajilla, located in the municipality of Doctor Coss in Nuevo León, Mexico. When Najo was 10, his mother moved the family to the nearby town of Mission, Texas, where she purchased a small tavern and operated it successfully for many years afterward. Najo lived in Mission for the rest of his life. The family's financial stability allowed the youth to spend much of his time playing the relatively new game of baseball, which was very popular along the Texas-Mexico border at the start of the 20th century.