Hera is the sister and wife of Zeus
(the Greeks did not approve of this arrangement for real people but they
thought it was okay for gods). (Compare the Egyptian
gods, who also marry their sisters). So Hera is also the daughter of
Earth (Rhea) and Time (Chronos).
Hera is usually thought of as responsible for marriage and the family, and Greek men thought of her as mean and selfish and generally unpleasant to be around. She's always getting mad at Zeus about something. But people did sacrifice to her, especially at a wedding.
Hera is the mother of Hephaistos, the god of volcanoes and blacksmithing. That's appropriate, because she is an Earth goddess and volcanoes are born out of the earth. She's also the mother of Hebe, the goddess of youth, and Ares, the god of war (maybe because she is associated with agons). Different Greek story-tellers disagreed about whether Hera's husband Zeus was the father of these children, or maybe Hera just made them on her own, with no father.
Throughout all the stories, Hera spends a lot of her time trying to get back at Zeus for having other girlfriends besides her. When one of Zeus's girlfriends has a baby, Hera hates that baby and tries to get rid of it. The most famous of these babies is Hercules, who was the son of Zeus and a human woman named Alcmena. Another famous story about Hera is the one about Echo and Narcissus - here's a video of it:
To find out more about Hera, check out these books from Amazon or from your library:
We Goddesses: Athena, Aphrodite, Hera by Doris Orgel and Marilee Heyer. For kids, with a feminist view.
D'aulaire's Book of Greek Myths, by Edgar and Ingri D'Aulaire.
Greek Religion, by Walter Burkert (reprinted 1987). By a leading expert, for adults. He has sections on each of the Greek gods, and discusses their deeper meanings, and their function in Greek society.