Spread across several episodes Ben and Adam have been following the breadcrumbs of the "real" Miles O'Brien who lives in a loveless marriage to Keiko.
Season 4 Episode 11 (Data's Day) O'Brien seems to be in an arranged loveless marriage to Keiko... the beginning.
Season 4 Episode 12 (The Wounded) O'Brien and Keiko, having just married, have an argument about breakfast. Neither of them know what the other likes.
Season 5 Episode 15 (Power Play) O'Brien is "possessed" by an alien and holds Keiko and their daughter hostage.
Season 6 Episode 2 (Realm of Fear) O'Brien keeps a poisonous spider as a pet while living with an infant.