There was a king named Pururavaa in Chandra Vansh who could traverse between Dev Lok and Earth. On one such occasion he saved Urvashee from miscreants, which made her fall in love with Pururavaa. Indra, granted a married life to her for some period.

Vaivaswat Manu was the son of Sun God from Sanjanaa. Vaisvaswat Manu's eldest son was Il (according to Matsya Puraan). When Vaivaswat Manu became old, he retired to the forest. Il was appointed the ruler in his place. Il set out on a voyage of conquest and traveled throughout the world. Winning like this he came to a forest named Shar Van (this is the same Shar Van where Shiv's son Kaarttikeya was born and Shree Raam also had His arrows from the same forest). It belonged to Shiv and Paarvatee. Shiv had decreed that any man who entered that forest would become a woman. King Il did not know about this rule and set foot in the forest inadvertently and as he did that, he immediately got transformed into a woman. Even his whole army got transformed into women. He even forgot all about his earlier life. He started wandering in the forest in the form of the woman, named Ilaa.

The Moon god, Chandra, had a son named Budh (the planet Budh). While Ilaa was wandering around as a woman, Budh came upon the Earth and fell in love with her. The two borne a son and he was named Pururavaa and thus Pururava became the first mortal ancestor of the lunar line (being born to Moon god's son).

Il Later Becomes Male
Meanwhile, Ikshwaaku (Manu's son born from his sneeze) and his other brothers started to look for Il. When they could find no trace of their brother, they asked the sage Vashishth, their Kul Guru, if he knew of Il's whereabouts. Vashishth used his mental powers to find out what had happened to Il. He found that Il entered the forest belonging to Shiv and Paarvatee and had becom a female. He asked the princes to pray to Lord Shiv and Paarvatee. The prayer, if heard, was the only way to make Ilaa a man once more. They did pray, and the prayers pleased Shiv. Shiv said - "Ilaa can never be made a man again. At best, we will alternate Ilaa between being a man for one month and a woman for another month." Although this arrangement was not a very good one but there was no other alternative, so as a man, Ilaa came to known as Sudyumn, Sudyumn had three sons named Utkal, Gaya and Haritaashwa.

King Brahmadatt Who Knew All Languages
King Kaushik had seven sons. They became the disciples of sage Garg. Once there was famine. During famine time Garg ordered his disciples to graze the cows on the near by hill top grass. Being very hungry they killed one of the cows after rituals and ate it. They lied to sage that one cow was eaten by tiger. So because of that sin,  they became seven hunters in the next birth with quality of Jaatismaar (who knows about is previous birth). The hunters fasted until death and they were born as seven deer. The seven deer too fasted unto their death and were born as seven birds.

During that time the King of Paanchaal by the name of Vibhraj came to that forest. One of the birds desired to be born as the son to King and other two desired to be born as sons of ministers of the King. The remaining four did not desire any thing and they were born as the sons of a Braahman. So the bird who desired to be born as the son of a king was born as Brahmdatt. In due course he got married to a princess Kalyaanee. This Kalyaanee was nobody else but the same cow that those princes had killed in their previous life while they were the disciples of sage Garg.

Brahmdatt could understand the language of all creatures on account of a prayer made by king Vibhraj. Once he made a big laugh hearing the conversation between two ants. The queen not knowing about his capacity could not make it out as why did he laugh so loudly and felt that he was laughing at her. She did not say a word but got restless. On that restless night Brahmdatt had a dream of Lord Vishnu that, he will understand every thing next day morning.

The four sons, who did not desire anything, were born to a Braahman and wanted to do Tapasyaa. They told their aged father that he need not worry about himself and the King Brahmdatt will help him, just tell him "Disciples of Sage Garg". The next day the Braahman approached the King and told "Disciples of Sage Garg". King Brahmdatt realized about his materialistic pursuits so he gave him as much wealth as he required and joined his brothers to do meditation. His two brothers born as minister's sons too joined him. Before proceeding to do Tapasyaa, King Brahmdatt declared his son Vishwaksen as the heir of the kingdom.

Are we referring him in Vishnu Sahastranaam?