Isis and Osiris were two of the four children of Nut, the earth goddess. Isis and Osiris were married. As the eldest child, Osiris ascended the throne and the people loved him, but his brother, Set, was jealous of this and sought revenge. Set killed Osiris, cut him into pieces, and disperse the pieces all over Egypt.
Isis, however, had great magical powers. She traveled across the land, collected all the pieces of Osiris, breathed life back into them, and resurrected him.
Soon, they conceived a child together, Horus, but Osiris could not return to the land of the living and went on to rule the underworld.