Familiar Faces

Familiar Faces is a quest in Fallout 4.

Quick walkthrough

 * 1) Talk to the Vault-Tec rep.
 * 2) Persuade him to join one of your settlement.

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

If you head to Hotel Rexford, and go up the stairs, you will find the Vault Tec rep, who is now a ghoul. When you talk to him he will immediately recognize you. Turns out 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 you keep on talking he will tell you that he is lonely and wishes he had a friend. You can invite him to Sanctuary Hills, to which he will respond by saying "Yes. But promise you will visit!". If you promise him you will visit he cheers up, and heads to Sanctuary.