- Kirayoshi O'Brien was born shortly before the Dominion War and moved to Earth at the conclusion of the conflict.
- He spent his childhood all over the quadrant with his mother, visiting places as far-flung as Bajor, Alpha Centauri, and Cardassia Prime.
- “First Contact Day”: The player visits the bridge of the Enterprise at Utopia Planitia and meets with Lieutenant Kirayoshi O'Brien and the rest of his crew.
- “A Step Between Stars” - Lieutenant O'Brien is among the Enterprise-F crew assembled at Dyson Sphere Joint Command prior to launching the mission to rescue and assist Admiral Tuvok.
- "Utopia Planitia: One Big Ship": Now a Lieutenant Commander, O'Brien welcomes Lieutenant Whetu and Ensign Elyos of Utopia Planitia aboard the Enterprise, which is undergoing a large-scale refit following the Iconian War. He cautions them that he has made a number of nonstandard modifications to the ship, and that they should consult him if they find anything outside normal specifications. He arranges to meet Whetu over dinner in ten-forward to discuss their progress.
- "New Featured Episode: 'Beyond the Nexus'": O'Brien is speaking with Captain Geordi La Forge of the U.S.S. Challenger in the shipyards of Earth Spacedock when Ensign N'vall of the Challenger approaches. She hands La Forge a PADD containing new orders - the Challenger is to embark on a mission to the Nexus. O'Brien offers to put La Forge in contact with an officer who may be able to help with the mission.
- Kirayoshi is the second child of Miles and Keiko O'Brien and was born aboard Deep Space 9. He has an older sister named Molly. Dialogue in the mission "Sphere of Influence" mentions that the Chief Engineering Officer of the Federation's flagship, the U.S.S. Enterprise-F, is named O'Brien. According to Kestral's writings in Star Trek Magazine and her dialogue prompts to Dave Rivas for "Sphere of Influence", indicate that this is Kirayoshi.
- In the Official Blog "Utopia Planitia: One Big Ship," it is revealed that O'Brien has received a promotion, and now holds the rank of Lieutenant Commander.
- Kirayoshi O'Brien at Memory Alpha, the Star Trek Wiki.
- Kirayoshi O'Brien at Memory Beta, the non-canon Star Trek Wiki.