Hephaestus is the god of forges and fire. He's the son of Hera - and only Hera, since she was trying to one-up Zeus after he had Athena.
Hephaestus sired several children by many different mothers; most were mortal but a few were minor gods. However, he and his wife Aphrodite had no children; Aphrodite's more well-known children were fathered by Ares.
When Hephaestus was born, he was so ugly that Hera threw him off Olympus. He fell for a full day before landing and breaking both legs. He was raised by sea nymphs until he was told of his parentage and somehow climbed Olympus, where he proved himself as a blacksmith. He made many of mythology's most famous objects, including Hermes' hat, staff, and sandals, as well as Aphrodite's girdle (really, a belt), Harmonia's necklace of beauty, and Achilles's armor.