Pie and Beans
Look for me on the local news, I'll be the guy arrested for trying to burn down a Nintendo exec's house.
Still waiting on someone to explain how my siblings and I all saw the same dude in our house in different times and contexts over a couple months, when we all didn't tell each other because we didn't want to seem crazy, until a random ghost discussion came up a couple years later. I guess a skeptic could assume it was that thing where you come up with fake memories or something, but it was a deeply novel and impressing experience for each of us before we ever discussed it. We came to the table with the details, we didn't hash them out together.
I'm not saying it was a spirit, but when you see a stranger in your house in the middle of the day and he fucking vanishes before your eyes before you can say anything to him because you thought he was a real person, that's a little different from a "sense of something there" or a blob in the dark. Either we all have a psychic bond to transmit the same hallucination to each other or something incredibly complicated went on.
Think of your house as the mechanism poking the backs of these volunteers. Everything about it, from the furniture layout, to the way its gravity affects you down corridors and stairs, all affecting you and your siblings in the exact same way from day to day. You've already established that the house felt old fashioned, and everyone has that imprint of the classical Victorian through 1920's ghostly chap to call upon at the front of your memories to whip out and apply to any humanoid apparition you witness, as caused by any vertigo or strange spatial awareness glitches.
Some places just feel spookier than others due to any number of variables from draft, light, and so on. The perfect collection of which will cause certain humans to react in the exact same way, cause a brain blip, and out comes the exact same information.
Its why the whole "going towards the light" thing exists, its why the whole sleep paralysis "demon on my chest" thing exists, and so on. Our minds are predisposed to being a bit shit at times and plopping entirely pre-constructed waking dream episodes on us from external influence or illness.