EDIT: IT SEEMED LIKE THIS POST IS A SPOILER POST. If there are any kind hearted mods out there, could ya please move it to the cheats/hints/spoilers section? ty.
on the hearthfire wiki it states, if you have 2 kids, one day one of them might come up to you and ask if he/she can keep an animal(e.g. fox).
Well, i never encountered this and my hearthfire home is there for a long time already. I do sleep there most of the time. I havent brought a dog home yet though.

Sometimes it takes awhile, so I've heard.