I'll tell ya all a small story. I liked "Carlotta Valentia" the gal with a daughter in Whiterun which sells produce; so I made her a follower with http://skyrim.nexusmods.com/mods/15524 (charmed I'd say), brought her home, gave her a maid dress and transformed her into my own personal maid and everything worked as intended. Then a week later, to my surprise, I found in my home, hanging around Carlotta HER DAUGHTER.
Now, take into account that in my game children are NOT essential (thanks to another mod) so my guess is that the AI package for Carlotta's daughter was to hang around her mother or something and as soon as the AI noticed I disrupted the routine of Carlotta decided to reunite mother and daughter, so probably had the child walk all the way through my house (which is located near riverwood),managed to survive the trip and all and had the daughter run around my home.

* AFT has a command to make any NPC a follower and have it controlled by the mod itself.

Wao, pretty cool. Now you are a happy family indeed. Can you arrange it to give her a little brother...?

Actually I was planning to take advantage of the non-essential child and to have the child take a one-way trip to a cliff *grin* but perhaps I'll modify my housemod to make room for both of them in the guesthouse.