Heat by Mike Lupica

Heat is a story about 12 year-old Michael Arroyo, who pitches for a South Bronx little league baseball team. He and his brother, Carlos, are recently orphaned after their father dies, and they lie about living alone to avoid being split up by social services. Michael has such a powerful throw that the coach on an opposing team thinks Michael is lying about his age, which would disqualify him to play, and ruin his chances to become a major league player. As Michael and his brother try to get Michael's birth certificate from Cuba, their secret gets harder to hide, and their lives get even more
complicated.