My apologies, maybe I misunderstood the comments about your siblings' experiences. When you said "while they were here," I took that to mean when they lived there some years ago before moving out as young adults. Now after reading your last response, I think you meant while they were in the house very recently visiting their sick mother. If so, then all the voices/noises, as well as the book reading apparition, have occurred since her return from the hospital. That would seem to indicate the activity is somehow a function of your mother.