Sarah Sisko was the biological mother of Benjamin Sisko and first wife to Joseph Sisko. They met in Jackson Square, New Orleans, Earth in June 2331. Two months later, Joseph and Sarah wed, and Sarah gave birth to Benjamin the following year.
Two days after Ben's first birthday in 2333, Sarah inexplicably walked out on her family. A despondent Joseph Sisko spent three years searching for her. When he finally located her whereabouts in Australia in 2336, where she was working as a holophotographer, he discovered she had died the month before in a hovercraft accident. Joseph later remarried and never mentioned Sarah to his son as he grew up, who assumed his stepmother was his real mother. Joseph did not reveal the truth to his son until 2375.
The Siskos eventually discovered that Sarah had been possessed by a Prophet and forced to give birth to their Emissary. When she regained control of her body, she left her husband and son. (DS9: "Image in the Sand")
The Prophet who had taken possession of Sarah's body later took her appearance when communicating with Benjamin Sisko. Notably, unlike the other Prophets she tended to call Sisko "my son", rather than "the Sisko." She also showed him tenderness, more so than any other member of her race.
In 2375, she contacted him in order for him to release the Prophets who had been imprisoned by a Pah-wraith. She revealed the existence of the Orb of the Emissary on the planet Tyree. Ben located the Orb and, upon opening it, released the Prophets, who cast the Pah-wraith from their home in the Bajoran wormhole. (DS9: "Shadows and Symbols")
The Prophet took Sarah's appearance later that same year in an attempt to talk Sisko out of marrying Kasidy Yates. Sarah was convinced that, if he went through with the marriage, he would "know nothing but sorrow." Despite her warnings, Benjamin went through with the wedding. (DS9: "Penumbra", "'Til Death Do Us Part")
The Sarah Prophet ultimately greeted Benjamin in the Celestial Temple after he had fulfilled his destiny and defeated the Pah-wraiths, but at the cost of losing his corporeal form. Sarah informed Sisko that his task was complete and that he must rest. And, that his greatest challenge was not in front of him but behind him Nevertheless, Sisko promised Kasidy – pregnant with his child – that he would return. (DS9: "What You Leave Behind")