Sage Vibhandak has been engaged in Tapasya (penance) since childhood, much to the chagrin of Indra. He can usurp heaven with his powers, thought Indra, so he sends Urvashi to distract Vibhandak. Urvashi successfully breaks Vibhandak’s Tapasya and blackmails him to bore a son with her. In return, sage Vibhandak gifts Urvashi his semen and tells her to impregnate herself. Urvashi’s primary mission is not to bear a son from the sage but to break his Tapasya. So when the mission gets accomplished, she transfers the semen to a deer- impregnating the deer. The deer soon delivers a human baby with deer horns, and thus Rishyasringa, “a baby with deer horns”, is born.
The incident of Urvashi makes sage Vibhandak develop extreme hatred toward women. Hence, he decides to raise Rishyasringa in an isolated part of a forest utterly devoid of any forms of feminine entities. Rishyasringa grows up without seeing any women and is unaware of their existence. However, under the guidance of his father, Rishyasringa gains unassuming yogic powers.
The forest where Rishyasringa is putting up comes under the jurisdiction of the kingdom of Anga, ruled by King Rompada. A time comes when the kingdom plunges into drought and severe famine. As things go from bad to worse, Rompada is told of an immense power radiating from within the forest, which could end the drought and bring prosperity to his kingdom. Rompada’s messengers bring him complete information about the father-son duo living an ascetic life in the forest. The king is also advised that Rishyasringa’s power could end his misery. Vibhandak, aware of the possible encroachments from the outside world, has ordered his son to rebuff any attempts from the kingdom and to strictly follow the “ Vibhandak line” which he has drawn around the forest.
To lure Rishyasringa out of the forest to the capital of Anga, Rompada sends his best courtesans. The courtesans of the king are scared of the sage’s wrath, so they do not approach Rishyasringa directly; instead, they build a hermitage in the forest and wait for sage Vibhandak to leave his son alone. Finally, they get a chance to talk to the young son of the sage. Ladies pique Rishyasringa as he has never seen or heard of anyone other than his father. In his innocence, the young sage develops friendships with the beautiful and expert courtesans of the king. The ladies feed him with sweets and indulge him with fineries and luxury in every possible way. The impressionable young sage is soon under their spell and one day leaves the forest and follows the ladies to the town.
Rishyasringa: brother-in-law of Lord Ram
As soon as the holy feet of Rishyasringa touch the kingdom of Romapada, the sky starts to pour rain, ending the long spell of drought. Romapada is happy with the outcome but equally fears sage Vibhandak’s wrath. To save himself and his kingdom from the sage’s curse, he offers his adopted daughter Shanta’s hand in marriage to Rishyasringa. Shanta’s biological parents are king Dasharath and his queen Kausalya, who are also the father and mother of Lord Ram. The whole incident happened before Lord Ram took the avatar.
After the marriage, Rishyasringa and Shanta return to the forest to lead a life of austerity. Later, king Dasharath humbly invited the same sage, Rishyasringa, to Ayodhya to perform a Putra Kameshti Yajna. As a result of the success of the yajna, Dasharath was blessed with four divine children in the form of Ram, Bharat, Laxman, and Shatrughan.
Source: Valmiki Ramayan and Mahabharat