Idas, with his inseparable brother Lynceus, was the son of Aphareus, king of Messenia, and Arene. His name suggests 'Ida', but we are not told of any connection with this famous mountain.

He was an adventurous (and headstrong) person, however, so perhaps his name relates to idea, 'form', 'manner', 'fashion'. Or again, as with Idaea, possibly ida, 'wood', 'timber' may be more fitting. (One incident involving a tree was when Idas' lynx-eyed brother Lynceus spotted Castor hiding inside an oak; Idas promptly killed him. This was the culminating stage of Idas' long-running quarrel with the Dioscuri.) Idas married Marpessa, who bore him Cleopatra (who married Meleager).