You know this pattern if your phone rings first every time something goes sideways. The building calls you about the leak. The neighbor calls you about the car in the driveway. The bank calls you about a letter. Your siblings hear about it afterward, secondhand, if at all. The load is real, but the routing has settled without anyone deciding it, and the routing is fixable.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Check where the calls actually went
Open your phone's call history for the last month and count the calls about Mom that came to you versus the calls that came to anyone else. Do the same for the texts. If the count is lopsided, the routing has already decided for the family. You are not imagining it, and it is worth writing the numbers down before anyone argues about fairness.
Check the names on every form
Make a short list of every place that has a contact for Mom: her doctor's office, her bank, her insurer, her building or property manager, the church office, the neighbor she trusts, the agency that visits the house. For each one, ask what name is on file and what phone number it calls. Mark the ones that point to you by default. You do not need to change them all in one afternoon, but you should know which ones are pointing at a single person.
When you do want to add a second contact, call the office and ask what the process is for adding one. Offices differ, and the question itself tells them the family is organizing. If something about authority to act is unclear, ask the office directly what it requires, and do not treat your own guess as the answer.
Build a call list you can hand over
Write one page. List who the office or company should call first, second, and third. Next to each name, say what that person handles: rides, bills, the house, the building, the doctor's scheduling. Questions about medicine stay with the family member named for the doctor's office, and the pharmacist answers pharmacy questions. Add what happens when none of the names picks up. Put the page where every sibling can see it, and send it to the offices that need it.
Test it once on purpose
On a weekday, call your own list the way a stranger would. Start with the first name and see who answers, then the second, then the third. The test shows you the routing you have, not the one you wrote down. If the first call still reaches only you, the page needs a different first name, and that is a conversation to have with the family, not a verdict on anyone.
If you want the starting order for the whole family before you change any contacts, begin with Start here.