I have never heard this before..Does your grandfather know these other people at your aunts work?

no he doesnt. my aunty works in a building thats kinda like a old folks home

Honey, I wish I had an answer or even an idea..If he sees this then maybe a movie has stuck in his mind and he has exagerated the image..I would think though that it would be good to let his doctor know just in case ther are more things going on..

Maybe do some research on sleep paralysis, it can cause hallucinations during sleep. It is very strange however that other people have seen the same things; perhaps there is some connection between your grandpa and the people at your aunts work, ex. maybe they watch the same tv show, or have wallpaper that for some reason stimulates similar visions? Look into finding some similarities between them, maybe something specific is triggering this.