tl,dr version: Guy who wandered in from the wasteland is treated as family when trying to hook up in the living quarters. Is this supposed to happen?
Story of this vault: Its my first Survival Mode attempt. Things were going well, got Butch in a lunchbox even. I was caught offguard by the frequency and damage potential of fires and radroaches. I had too many babies simultaneously and ran out of food and water, so my dwellers were half irradiated. Then a couple rapid raider attacks and vault fires and everyone is dead, except two children. Thankfully, they were from completely separate sets of parents. Instead of just starting over I am trying to recover. Those two kids are now the parents of the new workforce, they have had 4 boys and 1 girl. I've only had 1 person show up at the front door unexpectedly (the radio room has not yet been successful.) I was hoping that the new arrival would match up with the only daughter, but the two of them call each other family. His last name is different than both parents, not that that is how it is tracked by the code. So I guess he is a first cousin or something. This vault is going to grow very slowly if I can't bring in new blood...