He is the elder son of Agni who set forth to copulate with the wives of seven sages who were not the seven wives of seven sages. It’s a bit of a long story. The long and the short, Agni copulated with live reproductions createdby one god who then herself became inseminated. She spilled his seed, one version says, into the River Ganges and therefrom was born Kartikeya.
More available with free subscription. Email: email@example.com