THe story of Valli and Lord Murugan
He saw Valli in the fields and assumed the form of handsome tribal hunter. She asked him to leave as the chief was coming. After the chief left, he changed back into the hunter form and proposed to Valli but she refused. He then changed himself into an old man. He asked Valli for food & she gave him a mixture of millet flour & honey. She provided him with water too to which the lord jokingly remarked that she can quench his thirst for a companion too.
Their marriage - Lord Murugan
But that made her angry so the lord requested his brother Lord Ganesha for help. Lord Ganesha appeared as a wild elephant. On seeing the elephant, Valli ran back to the old man pleading to save her. Lord Murugan proposed to save her only if she agreed to marry him. In the heat of moment, she agreed & Lord revealed his true form. It was then that Valli realized that it was her beloved Lord, who was with her all the time. This is how they both got married.
Devasana and Lord Murugan
While Devasena was gifted in marriage to Lord Murugan by Indra after he vanquished the demons. Devasena was in her previous birth the daughter of Indra, the king of gods, who too did an austere penance to get wedded to Lord Murugan. The marriage with Devasena happened in the most orthodox way and is described as the Vaidika type of wedding. Thus, together with his two consorts, Lord Murugan teaches the highest philosophy of human life.