Tell your siblings you’re closing down the units. Give them a specific date and tell them anything they want needs to be removed from the units by that date. You don’t need a reason, and I wouldn’t entertain discussions about sharing payments either. At the end of that time, dispose of the items however you want.
I would keep the photos and family records and give away or sell everything else. Anyone who wanted to scan photos or documents would have to come to my house at my convenience. I don’t let the originals go and I’m not a copying service, so they’d have to scan them to my computer and bring a thumb drive to save them on.