Geb is the god of the earth, the solid ground, the source of fertility [S4]. He is the son of Shu and Tefnut and the husband of Nut (his sister) [S1][S4]. Geb and Nut are the parents of the four children who form the core of the Osiris cycle: Osiris, Isis, Set, and Nephthys [S1][S4]. The myth of Geb and Nut: Shu separated them, holding Nut up, because the earth-god and the sky-goddess were inseparable [S4]. Geb's domain is the fertile black soil of the Nile, the source of all life [S4].