He's the son of the sea god Njordr, and twin brother of Freyja.
Consorts & Children:
He's married to a giantess named Gerdr, for whom he gave up his sword that can fight by itself (but only if its wielder is wise). Because of this, he'll lack weapons when Ragnarok, the end of the world, arrives, and will be killed by the fire giant Surt.
Notable Stories Involving Him:
He's said to be the most attractive of the gods, as well as a peaceful but brave warrior. He's often called upon to bless a marriage with fertility, or to ensure a bountiful harvest. He rides a chariot drawn by a golden boar the dwarfs made for him, but also has a ship that always draws a favorable wind and can become small enough to fit in a pouch.
SOURCES: Wikipedia, Encyclopedia Mythica, & The Ultimate Online Resource for Norse Mythology and Religion