SB 6.14.30
sapi tat-prasanad eva
citraketor adharayat
garbham krtadyutir devi
krttikagner ivatmajam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As Krttikadevi, after receiving the semen of Lord Siva from Agni, conceived a child named Skanda [Karttikeya], Krtadyuti, having received semen from Citraketu, became pregnant after eating remnants of food from the yajña performed by Angira.