This is an excellent article by Richard Eisenberg that offers eight strategies for systematically paring down the stuff of aging parents that apparently nobody wants. It’s a necessary but ultimately awkward ritual of sorting with an eye towards aggressively casting aside articles that have both deep personal meaning but essentially zero value to the current generation.
It’s a fact of family life: roles are cut in stone. Stop trying to change a sibling who for the most part resents you for having the audacity to think you need to fix him or her.
Accurately assess what a sibling will and will not do for an aging parent. If their contribution is zero, then zero is is and move on.