Supernatural. Michael's Daughter.

Twin sisters Kelly and Kaida Kline are both innocent women, that get caught up in the deadly world of Supernatural as they both made a terrible mistake of sleeping with the devil, Lucifer himself and his brother, Archangel Michael. They both have children. Jack Kline the son of Lucifer and the first Nephilim. And his cousin, Alexandria Kline, the daughter of Michael and the first Nephalem (half angel and half demon) in existence. Two kids born to the two most powerful Archangel's. Michael and Lucifer.