The protagonist of "Heat" by Mike Lupica is 12-year-old Cuban immigrant Miguel (Michael) Arroyo. He is a Little League player with a pitching arm so good that rival Little League coaches ask about his birth certificate to prove he is only 12 and eligible to play.
Adults wish to speak to his father about his birth certificate, but Michael can't let anyone know his father died several months prior because his brother, Carlos, is only 17 and they are trying to avoid foster care by not letting people know until Carlos is 18. Michael is forbidden to play baseball until the birth certificate is produced. The plot resolves with a Cuban Yankee baseball pitcher using his contacts to find Michael's birth certificate so that he can play in a crucial Little League game and a Little League official taking temporary custody of Michael and Carlos until Carlos turns 18.