In Greek Mythology:
Ino was the daughter of the Theban King Cadmus, and his wife Harmonia. She also had several sisters, namely: Semele, Agave and Autonoe. Ino married, as his second wife, Athamas, who was the King of Orchomenus.
Athamas' two sons of his previous marriage persecuted her. Later she had two sons with Athamas: Learchus and Melicertes. She then decided to bring up the baby Dionysus, one of Zeus' and Semele's children, because Semele had been burnt up by Zeus' thunderbolt. Ino and Athamas disguised Dionysus as a girl so that Hera would not find out (she was jealous of Zeus' illegitimate children). Hera did find out and therefore decided to punish Ino and her husband by driving them mad.
In her madness, Ino thought that her own son, Learchus, was a deer, and consequently hunted and killed him. She then put her other son, Melicertes, into a cauldron of boiling water and jumped into the sea, holding it, killing both herself and him.
A dolphin carried the body of Melicertes to the shore, where it was found by his uncle, Sisyphus, who decided to found the Isthmian Games in honour of his dead nephew.
Dionysus transformed Ino and Melicertes into sea gods (Leucothea and Palaemon). They lived with the nereids and helped sailors in trouble, for example Leucothea saves Odysseus in the Odyssey.
Euripides, however, gives a different story of Ino. In this she deserted her husband and sons and went to join the Maenads. Athamas therefore got married again, this time to Themisto, and they had two sons together, Sphincius and Orchomenus. Ino later returned, but Athamas keeps her in secret as a nurse for the children. Themisto then wanted to kill Ino's two children, and told who she thought was the nurse her plan and also to help her carry it out. She told her to cover Ino's two children (Learchus and Melicertes) with black blankets that night, and her two children (Sphincius and Orchomenus) with white ones. The 'nurse' did the opposite as what she was ordered, and when Themisto found out, she killed herself.