Kirayoshi O ' Brien Kirayoshi O ' Brien was born in 2373 , the second child of Miles and Keiko O ' Brien . Kira Nerys acted as a surrogate mother for Kirayoshi after Keiko was injured during a mission to the Gamma Quadrant in late 2372 , carrying the baby to term . Kirayoshi ' s name was often shortened to " Yoshi . " Conception . Kirayoshi was conceived in 2372 . Miles found out Keiko was pregnant again after Keiko and Molly arrived back from a trip to Bajor . It was Molly who told her father that she was going to have a little brother . Miles initially believed she was talking about her doll , but after Molly pointed to Keiko ' s stomach , he realized what she meant . ( ) The news quickly spread around Deep Space 9 . Julian Bashir gave his congratulations and he and the expecting parents celebrated with a drink at Quark ' s . Worf also learned of the news and , recalling his reluctant role during the birth of Molly , told O ' Brien that he would be away from DS9 at the time Kirayoshi was born ( " " Far away . Visiting my parents . On Earth . " " ) . ( ) Transferral and development . Several months later , Keiko and Kira Nerys were involved in an accident aboard a runabout in which Keiko was critically injured . In order to save both mother and unborn child , Julian Bashir transferred the baby to an undamaged womb – namely , Kira ' s . Although the procedure required various hormonal injections in order to allow Kira ' s Bajoran body chemistry to cope with a Human infant , it proved generally successful ; however , due to the dense blood vessels that form between the mother and baby during a Bajoran pregnancy , Kira would have to carry the baby to term as a transfer back to Keiko would prove too dangerous for Kira and the baby . Thereafter , Kira moved in with the O ' Briens so that they could continue to feel close to their unborn child . ( ) The Cardassian Silaran Prin intended to remove Kirayoshi from Kira ' s womb several weeks before he was due to be born , wishing to differentiate himself from Kira ' s old resistance movement by refusing to harm the ' innocent ' . Fortunately , the makara herb s she had been taking counteracted the effects of Prin ' s merfadon , which enabled Kira to stop him . ( ) Birth . Kirayoshi was delivered in a traditional Bajoran birthing ceremony in early 2373 . Miles , Keiko , Shakaar Edon , and Y ' Pora , a Bajoran midwife , were at her side ; Kira later expressed some sorrow that she was not able to raise the baby herself , having genuinely bonded with the child during her time as a surrogate . ( ) Early life . Several weeks after the birth , Kira claimed that Kirayoshi recognized her , although a skeptical Jadzia Dax believed he was too young to " " even recognize his own finger s . " " Even after Kira told her that Kirayoshi smiled every time she entered the room , Jadzia retorted that it was " probably just gas . " ( ) Later that year Keiko had to go to Bajor , leaving Miles to look after Kirayoshi and Molly . He found that no one could look after Yoshi without the baby bursting into tears . Jake Sisko was one such unsuccessful babysitter . Miles later found that Yoshi slept better in the pit in DS9 ' s operations center . He believed it was the " pattern of lights . . . the hum of the optronic emitter s , or the vibration of the ODN relay s " . Miles later found that Worf had a calming effect on Kirayoshi ; Worf would sing Klingon nursery rhymes to Kirayoshi while babysitting him . ( ) Tekeny Ghemor thought Yoshi was " a beautiful baby " when he visited the station just before his death in 2373 . Owing to his complicated fatherlike relationship with Kira , he said he felt that , in a strange way , Yoshi was the closest thing he had to a grandson . ( ) Kirayoshi had not begun to walk by late 2373 . ( ) Before the Dominion takeover of Deep Space 9 and the start of the Dominion War , Keiko took Molly and Yoshi to Earth for their safety . ( ) When Molly O ' Brien was lost in time in 2374 , Worf took care of Kirayoshi , in an effort to prove to Jadzia that he was well suited as a father , as Miles and Keiko tried to reintegrate Molly into the family and station life . Although Worf felt briefly disheartened after he accidentally bumped Kirayoshi ' s head during a Klingon game , his mood improved when he learned that Kirayoshi was enthusiastically repeating the phrase " gung - gung - gung " , part of a Klingon exercise called " Hehh - duHpp " that was traditionally taught to Klingon children , which Worf had played with Kirayoshi during his time babysitting ( ) . Kirayoshi moved back to Earth with his family in late 2375 , when Miles accepted a position as Professor of Engineering at Starfleet Academy . ( ) Appendices . Background information . Kriayoshi was portrayed by Clara Bravo . Kirayoshi was presumably named partly after his surrogate mother , Kira Nerys . Yoshi ' s root meaning is " good " and is used as a prefix / suffix in names . " " Yoshi ! " " is also said in a way meaning " " Yes ! All right ! Good ! " " In ultimately omitted dialogue from the second draft script of " Accession " , Kirayoshi was predicted , prior to birth , to be male , tall , left - handed , and have curly hair like his father ' s . According to the script for " Business as Usual " , his name was pronounced as " keer - uh - YOE - shee " . " " Apocrypha . In " Star Trek Online " , Kirayoshi O ' Brien is a Starfleet Lieutenant stationed at Memory Alpha . He later becomes Chief Engineer of the " Enterprise " - F .