Milayn was a Trill female and the eldest daughter of Lela Dax and Nareeya. She had several other siblings.
In the 21st century, Milayn joined her family on Andevian II while her mother was teaching there. While the family was on the planet, a deadly disease broke and thousands began dying. Milayn, only twelve years old at the time, contracted the disease and died, before her mother could see her. Lela took her daughter's body back to Trill when the Andevians sent them home. (DS9 novel: Wrath of the Prophets)