Adonis was the Demigod Son of Apollo and the mortal Myrrha. He is the God of Beauty and Multiple Lovers. Before he was born, her mother was discovered by her father, a king, to be having sex out of wedlock. He chased her out of the kingdom in disgust and threatened to kill her. Aphrodite took pity on Myrrha and turned her into a myrrh tree. Two months later, Apollo delivered an infant Adonis from the tree and, at Aphrodite's request, allowed the goddess to raise him.
Unfortunately, Ares detested his lover having a mortal child to raise. On more than one occasion, he attempted to murder the young Adonis and regain Aphrodite's attention. Finally, Aphrodite asked Persephone to assist in raising Adonis as to quell Ares' anger.
When Adonis was grown, he proved to be as beautiful as an Olympian. So beautiful that both Aphrodite and Persephone fell in love with him. The two women, both of whom he was close with, wanted his attention. Finally, they brought the matter to Zeus and demanded that he make the decision.
Zeus proclaimed that Adonis would spend one-third of the year with Aphrodite and one-third of the year with Persephone. The final third would be spent as he chose. Adonis loved both goddesses and alternated spending the final third with Aphrodite and Persephone.
Both goddesses were deeply in love with Adonis and they did what they could to be close to him. He was a fan of hunting, so both Aphrodite and Persephone--neither of whom often hunted--took up the pastime to be with him.
Eventually, Ares grew enraged at Adonis' continued presence and attempted to kill him. However, before he died, Aphrodite found his dying corpse and brought him to Mount Olympus. She had him made an immortal god.
Since then, he has split the year in two and spent six months with Aphrodite and six with Persephone as their immortal lover. In the years since, Ares, Hephaestus, and Hades--all of whom disliked his presence at first--have grown to love and care for him as a member of their households. He holds a place of esteem with all of them.