Demeter - her name means "Mother Earth" - is the goddess of harvest and the fertility of Earth. Her daughter Persephone was abducted to the underworld by Hades. Because of Demeter's grief living things ceased their growth, and then began to die. Zeus tried to help them, but Persephone tasted the pomegranate seeds of Hades, so she must stay one third of the year there, in the underworld. When she comes back to her mother, Demeter is happy, and everything on Earth is flourishing. But when Persephone must go back to Hades, winter comes, and plants will not grow again until Springtime. That was the origin of seasons.
Demeter has a son too, Ploutus, the god of wealth. He was engendered when Demeter was making love with demigod Iasion, with whom she lay in a thrice-ploughed field.
Hestia - the goddess of home fire, heart, and a the right order of domesticity - is the kindest of all goddesses. When both Apollo and Poseidon tried to marry her, to save the peace, she decided to stay virgin. She is modest and trustful: Zeus assigns Hestia a duty to feed and maintain the fires of the Olympian. She was rarely depicted on paintings or statues, but she was important for both the households and the city: a small offering was made to Hestia before any sacrifice ("Hestia comes first"). With the establishment of a new colony, flame from Hestia's public hearth in the mother city would be carried to the new settlement.