Hades is a god of the under world/earth.

Demeter a goddess of the upper world/earth.

So, both deal in the earth, one below one above.

Hades was later associated with plant life and growth, for when Persephone rose from the underworld he had released spring.

Hades and Demeter were brother and sister, their mother was Rhea, and father Cronus.

At first, no. She was very upset at him. But he grew on her, and I firmly believe that she does now love him. After all they are the only couple of the Greek gods and goddesses that have never cheated on each other.

Like, yes. Love? It was an arranged marriage, so I dont think love was even an issue.

Overview

Persephone was the daughter of the grain goddess, making her a fertility deity; she was abducted and married by Hades, the lord of the dead.

The myth

Persephone, daughter of Demeter and Zeus, was said to be the most beautiful of the goddesses, rivalling even Aphrodite. Apollo, Ares, Hermes- all asked for her hand in marriage, but Demeter refused them, seeing her daughter's person as sacred.

Hades, lord of the dead, fell in love with her; and rather than ask her mother, he asked Zeus, who would neither give nor withhold his permission. It seemed the politically correct thing to do; he couldn't refuse his sister, a powerful goddess, or his brother, who was as strong as he was.

Demeter went to visit her mother Cybele, and left Persephone in Enna Vale (which is thought to be near Mt. Aetna in Sicily); Aphrodite, having heard of Hades' plan, decided to help it along. I suspect she was jealous. Whatever her reasons, she lured Persephone out of the house, and they wandered through the vale. Persephone strayed farther than the rest. Zeus caused a flower to spring forth- a narcissus, black and violet and silver, to ensnare his daughter. Persephone saw it, and went to pick it; and when she did, the earth split beneath her feet, and Hades sprang out. He grabbed her and dragged her down into the earth. (1)

Demeter returned home and found her daughter gone. From then on, she refused to let the earth be fertile, until someone would tell her where Persephone was. Zeus forbade the other gods to tell her, on pain of suffering Hades' displeasure- Demeter would surely take Persephone back if she knew. Helios, or in some versions Hecate, was the only one who would tell her. Demeter blighted the earth, and mankind was on the brink of extinction.

Zeus sent Hermes to reclaim the girl. Before Hades would give her up, he tricked her into eating a pomegranate seed, thus binding her to the Underworld. (2)

Demeter, Persephone and Zeus eventually struck up a bargain: Persephone would spend six months with Hades, six with Demeter. (3) This is the origin of the seasons.

Meanings of the myth

The most obvious interpretation is that it is a nature myth- Persephone's transitions between the realms of life and death represent the growth of plants in spring, and their death in autumn/winter. Culturally, it can be seen as the origin of the ancient Greek and Roman marriage custom, where the groom would ritually "abduct" the bride from her mother. It can also be seen as a resurrection myth, similar to that of Dionysus returning from the Underworld with his mother; however, since Persephone always goes back to the dead, it would more likely represent reincarnation: Persephone as a life-death-rebirth goddess, similar to various Celtic deities and heroes.

Notes:

(1) Most sources would suggest that Persephone was physically raped, but to automatically assume that disregards the original meanings of the word. It derives from the Latin "rapere", to seize or grab; I think that such titles as "de raptu Proserpine", or the Rape of Persephone, merely refer to the fact that she was abducted.

(2) The number of seeds is debated. Some say it was only one, some say four, some say six.

(3) Again, the number of months varies in correlation with the number of seeds, as do the exact terms of the bargain. With one or six seeds, the usual agreement is six months with each; with four seeds, it was agreed four months with Demeter, four with Hades, and four serving as Zeus' handmaiden. I hold with the six-seed, six-month theory.

Persephone was the daughter of Demeter, goddess of harvest.
Persephone is a Roman goddess, daughter of Zeus and Demeter. Pluto(Hades) was in love with Persephone and abducted her against her will. It is said that Zeus advised him to do this because he knew Persephone's mother would not allow for the two of them to be together. When Demeter found out about the abduction, she forbade the Earth to produce. Eventually, Zeus was forced by the pleas of the hungry to force Hades to return Persephone so that the Earth could once again provide food.