Shaun ( synth ) Shaun , also known as S9 - 23 , is a prototype synth created by the real Shaun and lives in the Institute , unless the Sole Survivor opts to destroy the Institute during the mission The Nuclear Option , after which he can be sent to the Commonwealth or left to die . Background . Shaun was created at the behest of Father , the director of the Institute , and is a Gen 3 synth based on the real Shaun ' s DNA . Madison Li expressed discomfort and irritation according to her personal holotapes as Advanced Systems has been tasked with the creation of Shaun . She was unable to understand the scientific need for the creation of a child synth , something that Father did not bother to divulge . In actual fact , Shaun was created not for any research or scientific advancement , but simply on the whim of Father . When the Sole Survivor arrives to the Institute to locate their child during Institutionalized , they are briefly led to believe that the synth Shaun is the real one in order to test the child ' s responses . Shaun responds negatively and calls for help from Father before being deactivated . Father then acknowledges that it is still a prototype and does not work well . Interactions with the player character . Other interactions . If the player completes one of The Nuclear Option quests , and synth Shaun is not left behind in the Institute , he will ask the player character to bring items ( e . g . a hot plate ) so he can ' take it apart ' and in return will build useful items for the player character , such as weapon mods and the Wazer Wifle . Additionally , the player character can ask Shaun to live with them , and can send him to a number of locations , similar to a companion , although he is not able to be assigned to beds , like many other NPCs . He cannot be commanded to move throughout the settlement . He will stay within the confines of a small area ( e . g . near the Minutemen Radio Operator in the Castle ) . If the player instead completes the Nuclear Family quest , Shaun will be interactable and found within the Advanced Systems Lab . The player has the ability to choose where Shaun will live by talking to him . If you subsequently decide to move him to another settlement , it must be done via the workshop interface . Shaun will sometimes ask for all sorts of parts in order to build something . Effect of player ' s actions . After The Nuclear Option , if Shaun is not left behind in the Institute , upon meeting with the player character again and being interacted with , he will give them a holodisk named Shaun ' s holotape as instructed by Father , saying " I didn ' t listen to it , so I dunno what it says , but I think it ' s important . " The holotape , recorded by Father , reveals that he re - programmed Shaun to believe that he was the son of the player character , and pleads with the player character , saying " " I would ask only that you give him a chance . A chance to be a part of whatever future awaits the Commonwealth . " " However , if the player chooses the Nuclear Family option , they can still obtain the holodisk , but Father ' s speech will differ , still revealing that he reprogrammed Shaun and saying " " Both he and you deserved a chance to . . . To be a family . Please , take care of him . " " Should the Sole Survivor leave Shaun in the Institute following the sabotage of the reactor , he will go down with the facility - although if the Survivor sides with the Railroad and chooses to abandon Shaun , Tinker Tom will say he will still teleport Shaun out of the Institute and have the child taken care of ( as the Railroad ' s main objective is to free all synths ) . Whatever the case , Shaun never appears in the game again . Appearances . Shaun appears only in " Fallout 4 " .