Poseidon married Amphitrite, who was a Nereid, according to Greek mythology. Poseidon was god of the sea and brother to Zeus and Hades. Each god had his own realm. Like Zeus, Poseidon's love life was characterized by many extramarital affairs.
The Nereids were a band of 50 sea goddess sisters named after their father, Nereus, who was a gentle god of the sea. Amphitrite and her sisters normally lived in the depths of the oceans but would come to the surface to play sometimes.
Poseidon is said to have carried Amphitrite off with him while she was playing with her sisters, according to Encyclopedia Mythica. Amphitrite and Poseidon gave birth to a son, Triton, a half-human, half-fish god. Poseidon also had an affair with Medusa to produce the winged horse Pegasus and raped Aethra to produce the hero Theseus.