Consorts & Children:
He's husband to his sister Nerthus, and father of the twins Freyja and Freyr. Prior to that, though, he was married to the giantess Skadi.
Notable Stories Involving Him:
As god of the sea, he presides over good fishing, fair winds, and seafaring in general. Little is known about him, beyond his first marriage. His first wife Skadi was angry over the death of her father Thiazi, and so demanded retribution from the gods. However, they managed to instead convince her to choose a husband from among them, going by only their feet. She picked a pleasant-looking pair, thinking they belonged to Baldr, only to get Njordr. After they married, she was unhappy at his seaside palace, so he offered to spend half their days at her father's palace in the mountains. Neither turned out to be happy with the arrangement, though, and so parted ways.
Njordr Around the World:
He's the Norse counterpart of the Greek Poseidon or Roman Neptune.
SOURCES: Wikipedia, Encyclopedia Mythica, & The Ultimate Online Resource for Norse Mythology and Religion