Sibling moved in with parents, who developed severe cognitive decline over the last years of their lives. She manipulated them into believing all other adult children were out to put them away and take all their money, which was simply untrue, only her machinations, which included disparaging siblings not only to parents, but also to relatives and mutual friends and acquaintances. Some of them believed her. Besides her, we are four other surviving adult children. We aren't interested in any legal battling (no one even has funds for that), just want to know what's going on with possible sale and distribution of assets, etc, and what our options to follow up might be. She has made herself (somehow) sole authority and voice in any of these matters since our mom passed in 2019.
If there is no will or trust, then your parents died "intestate" (not interstate), or without a will. The courts will decide who is their representative, not you and not Sis. No one can sell or distribute anything until probate court decides who has the authority to do so. It is illegal to do otherwise. (You might remind your sister of that fact.)
You and your siblings need to consult a trust and estate attorney to find out what the next step is, because right now everything is legally in limbo.
I honestly think that the Sister who is doing direct care SHOULD have the authority, but that's me. Were I to want relationship or access I would offer what help I could with cooking, cleaning, respite care, and etc.
Contact an attorney to get answers for your state. Best of luck to you.
It is likely time for the four of you to spend about 100.00 each for an hour of a lawyers time. You will find out how to follow up on probate, finding out who is on the deed to the home (if there was one) and etc. in your area. You will then know how best to proceed about having an executor appointed to do a probate, if there is not will or trust.