(covers information from an alternate timeline)
In an alternate timeline, Miranda O'Brien was the descendant of Miles O'Brien and Rita Tannenbaum, officers from the USS Defiant. She lived on the planet Gaia with the rest of the descendants of Defiant's crash survivors.
When Odo changed the flight plan of the Defiant to avoid the crash that would strand the crew and preserve this alternate timeline, Miranda was wiped out of existence along with the rest of the descendants. (DS9: "Children of Time")