In Greek mythology, Callileon (Ancient Greek Καλλιλέων) is one of the sons of Thyestes by a Naiad nymph. With his brothers Aglaus and Orchomenus he is slaughtered by Atreus at Zeus' altar and served to Thyestes in the infamous banquet that seals the curse on the house of Pelops.
Adapted from Wikipedia, "Thyestes" · CC BY-SA 4.0
I.Victim of Atreus' banquet
Apollodorus (Epitome 2.13) has Atreus lure Thyestes under a pretence of friendship, then slaughter the sons Aglaus, Callileon, and Orchomenus — suppliants at Zeus' altar — boil them, and serve the flesh to their father without the extremities. The crime is the classic "Thyestean feast" that drives the next turn of the Pelopid curse (Pelopia, Aegisthus).
Wikipedia's Thyestes article narrates the same banquet; its family list uses the spelling Calaeus for the third son. The atlas keeps Apollodorus' Callileon as the id and name.
II.Homonym care
Callileon is this Thyestid child alone — not a separate Trojan or Argive namesake. Thyestes himself and Atreus remain separate character nodes.