Luv and Kush were the twin sons of Sri Ram and Mother Sita and their story appears in the Ramayana. The Jayanti is celebrated to commemorate their day of birth in the Ashram of Sage Valmiki.
Legend and History
Although Luv and Kush were familiar with the story of Lord Rama and Sita, they were unaware that they in fact were the sons of Lord Rama. They were also unaware of the true identity of their mother and the fact that she was abandoned by her husband because the people of Ayodhya had raised questions about her chastity after being abducted by Ravana.
Once, when Lord Rama had organized the Ashwamedha Yagna, the twins captured the horse when it was loitering around the Ashram. When the great warriors of Ayodhya learned of this, they came back to claim the horse, which the twin brothers refused to return. A battle ensued between the warriors of Ayodhya and the twin brothers in which even the might brothers of Rama, Lakshman, Bharata and Shatrughna were defeated.
Upon hearing this, Lord Rama was forced to enter the battle himself. He was impressed by the strength and valor of Luv and Kush and invited them to his palace. There he learnt of their true identity and also asked his wife Sita to return to the palace. Upon reaching Ayodhya she once again pleaded her innocence and asked Mother Earth to usurp her into her fold. Mother Earth obliged and swallowed her. The anguished Lord Rama took Samadhi in the River Sarayu to meet Sita in heaven. After the Samadhi of Lord Rama, the Ayodhya dynasty was carried down by the brothers Luv and Kush.
Another legend has it that Sita gave birth to Luv shortly after she started living at the Ashram of Valmiki. One day she wanted to go to the forest to collect wood. She left her son Luv under the care of Sage Valmiki and left. Soon after, the sage got busy with his chores and the little one crawled into the forest. When the sage realized that the infant was missing, he was exasperated. He did not have the heart to tell Sita that he had lost her only child. Therefore, he created another look alike of Luv from Kusha grass.
When Sita returned, Sage Valmiki was surprised to see little Luv in her arms. In turn, Sita was surprised to see the identical twin. Since, he was made of Kusha grass, he was named Kush and continued to live at the Ashram with Sage Valmiki, Sita and his twin brother Luv.
These are the two most important legends associated with the stories of Luv and Kush. These stories are recited on the Luv Kush Jayanti in most places to commemorate the birth as well as the bravery and strength of the young lads who serve as an inspiration for the youth.