According to 1 Maccabees, Mattathias had five sons.
They were John Gaddi, Simon Thassi, Judas Maccabeus, Eleazar Avaran, and Jonathan Apphus. Mattathias was a Jewish priest from Modi'in whose defiance of Seleucid religious policies helped ignite the Maccabean Revolt in the 160s BC.
The five sons did not all play identical roles. Judas became the best-known military commander after Mattathias's death. Simon served as a senior counselor and later became the final major leader of the revolt's founding generation. Jonathan succeeded Judas, while Eleazar and John also participated in the struggle and died during the conflict.
A common mix-up comes from counting only the most prominent leaders—Judas, Jonathan, and Simon—or from treating Mattathias's father and descendants as part of the same group. The question asks specifically about Mattathias's sons named in 1 Maccabees, making five the canonical answer.