The children of Vaivasvata Manu were the founders of the distinguished royal families of ancient India.Just as the major line of Sūryavaṃśa (Suryavamsa; the Solar dynasty) emerged from Ikṣvāku, from Ila-Sudyumna or Ilā, the other son of Vaivasvata Manu. In Mahābhārata- Rāmāyaṇa or Purāṇa, the account of Ila or Ilā has been described in details, and there are differences among several versons of the account. Ila or Ilā is an enigmous character of Mahākāvya and Purāṇa. It cannot be said properly whether she is the daughter of Manu, or his son– Ila or Sudyumna. The use of feminine gender in her name Ilā creates the mystery– Whether s/he was a man or not.
The seed of the famous Candravaṁśa was planted in her womb. Sired by Vudha, son of Candra– Pururavā is the son of Ilā, as a woman. In several legends regarding his/her gender-identity narrated in Mahābhārata and Purāṇa, she is presented as a woman, and she is the mother, not father, of Pururavā. There lies the significance of Ila or Ilā.
In Mahābhārata, Ilā has been mentioned as the eighth progeny of Vaivasvata Manu. It is to be noted that this progeny of Manu is called Ilā, not Ila. In Mahābhārata it is said that Pururavā was born of this Ilā. The poet of Mahābhārata has decribed Ilā as both the parents of Pururavā–
pururavāstato vidvānilāyām samapadyata
sā vai tasyābhavanmātā pitā caiveti naḥ śrutam.
Nīlakaṇṭha, the commentator of Mahābhārata, has explained that Ilā was actually the mother of Pururavā. But since she became a man afterwards, and came to be known as Sudyumna, and her on Pururavā was enthroned to her/his kingdom– so Ilā can be called Pururavā’s father as well.
mātaiva lavdhapumbhāvā rājyadānāt pitā’pyabhūt
mukhyaḥ pitā tu vudha eva.
From the legend narrated in Viṣṇupurāṇa and Bhāgavatapurāṇa. In these Purāṇa(s) it is said that a daughter named Ilā was born of the womb of Śraddhā, wife of Vaivasvata Manu. During the yajña performed with the purpose of getting a son, Śraddhā wished for a girl-child while offering the āhuti in fire. When the girl was born, Vaivasvata Manu was dissapointed. The priest Vaśiṣṭha then consoled him, saying that– this daughter will be a man in future, and will be known as Sudyumna. In other Purāṇa(s) it is said that Ilā attained manhood by the grace of Mitrāvaruṇa– this account is more or less supported everywhere else. It is also clear from the Purāṇa-description that Ilā was the eldest offspring of Vaivasvata Manu.
After attaining manhood, Ilā came to be known as Ila or Sudyumna. In Rāmāyaṇa, no such narrative is found that Ila was born as a daughter. Here the king named Ila is referred to as the son of Kardama Prajāpati. According to Rāmāyaṇa and other Purāṇa(s), Ila-Sudyumna went to a forest for hunting. Wandering across several forests, he finally reached a beautiful woodland where God Śiva was enjoying his divine consummation with Goddess Pārvatī. God Śiva had it decided, if any male creature enters the woodland during their happy time, would turn into a woman. Now, entering into the forest, Ila turned into a woman. She could remember nothing about her past life as a man. Without any purpose or destination, she started roaming about the forest.
Matsyapurāṇa has related that, Vudha found the beautiful Ilā roaming aimlessly about the forest, and got attracted towards her. He also understood that she had lost her memory. So he approached her, and said, “You are my wife, Ilā. Why are you roaming like this, leaving your household duties?” Ilā believed in these words of Vudha and started living in his house as his wife.
Now the ministers and associates of the king Ila-Sudyumna went on searching him, and they found the horse of the king– now the horse had become a mare,because it had also entered the private woodland of Śiva-Pārvatī. The king’s associates informed Vaśiṣṭha about this wonderful matter. Vaśiṭha appealed to Mahādeva about the condition of Ilā.
God Śiva said to Vaśiṣṭha– Ilā would not be a man completely once more. But after this, s/he would be a man for one month and a woman for the next month. As instructed by Mahādeva, Ikṣvāku performed a yajña for Ila-Sudyumna, nd as a result of that yajña, s/he would live as a man and a woman alternatively. In Matsyapurāṇa, this condition of Ila has been called the kimpuruṣa state– dattvā kimpuruṣo vīraḥ sa bhaviṣyatyasaṃśayam.
In the meantine, Ilā, as wife of Vudha, gave birth to Pururavā. But Ilā did not get the kingdom because of her turning into a woman. His/her younger brother Ikṣvāku ascended the throne. After the birth of Pururavā, Vudha, son of Candra went back to the heavenly abode. Ilā nurtured Pururavā and afterwards performed his corronation as the king of Pratiṣṭhānapura. AS described in Purāṇa, Sudyumna had three other sons called Utkala, Gaya and Haritāśva, and they established separate kingdoms. Pururavā was perhaps younger to them. So these sons were born before he became a woman. At the end of his life, Kimpuruṣa Sudyumna, after establishing the sons in their respective kingdoms, went back to that place where s/he lived with Vudha, as Ilā. Pururavā was born there. That place later came to be known as Ilāvṛtavarṣa.