Someone could of been walking when they didn't notice or you could hear the sound from next door if your house is connected(pressed up against).
Interesting. Shutters can do anything if the wind is blowing just right Now it would be even more interesting if the stairs were carpeted with a thick plush shag. Heating of the sun or cooling of the day has an affect on the wood of the house just in the temperature change.
Also heater pipes make unusual sounds. Had any alcohol been consumed by sis and mom when these incidents occurred? Are these people in their "right mind" or did some sickos get out from the "HOME.
Could just be haunted, plain and simple : D.
Could be people walking. Shutters being blown by wind. Imagination(Well not really, since multiple people heard it) Well thats all I can tell.
Sounds like just a harmless spirit wandering your house. You probably live in older home and there's a spirit of someone that died there present now. As long as it doesn't do anything mischievous there's nothing to worry about.
About everyone have these issues. Just ignore it, it isn't purposely scaring you in any way. If it was, you'd know.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.