In the quiet hours of the evening, if one stands at the base of the stairs in the dining room one can hear the faint sound of a child singing.
Both children are sound asleep and, should one choose to investigate, one would discover that the singing isn't coming from either of their rooms.
Sometimes, on a chilly autumn night, the smell of pipe tobacco smoke wisps by in the upstairs hallway.
Footsteps can be heard on the stairs when all creatures great, small, and furry are tucked in for the night.
I don't begrudge them coming in from the cold. But I'm much more comfortable with them when there's another flesh and blood and, more importantly, fully on this side of the Wall, human in the house with me when they do choose to visit.