Alonzo is the 7-year-old son of Mateo, a former colleague of Caleb's. His former Coast Guard father is quite strict with him, especially compared to how his older sister Ariana is treated. His younger brother is Dante. Alonzo was the lower elementary school chess champion, beating a third-grader for the title.
He comes to the Fairns' Fourth of July barbecue in 2013 because his parents are considering becoming Wynter's emergency caregivers, where he plays a game of chess with Jesse who engineers the game to end in stalemate (02 Out of Tune).