Familiar Faces

Familiar Faces is an unmarked quest in Fallout 4.

Detailed walkthrough
Talk to Daisy in Goodneighbor. If the Sole Survivor goes deep enough into conversation she will tell them that she was alive before the Great War. She will also tell them about another ghoul in Hotel Rexford, who states that he was also around before the Great War.

If the player character heads to Hotel Rexford, and goes up the stairs, they will find the Vault Tec rep, who is now a ghoul. When the player character talks to him, he will immediately recognize them. It turns out that because his name was not on the list to get into Vault 111, he had to suffer through radiation, turning him into a ghoul.

If the player character keeps on talking, he will tell them that he is lonely and wishes he had a friend. They can invite him to Sanctuary Hills, to which he will respond by saying "Yes. But promise you will visit!" If the player character promises him they will visit he cheers up, and heads to Sanctuary.

Companion reactions

 * Curie, Robert Joseph MacCready, Nick Valentine, Codsworth, Piper and Preston like when the Sole Survivor recruits him to their settlement.
 * Cait, Danse and Hancock disapprove of the Sole Survivor recruiting the Vault-Tec rep to their settlement.