Its different in every family, but just asking the other siblings for assistance might be beneficial. With my mom, I was the closest and had the most interaction over the last couple years. Once it was determined that mom was not capable of going to doctors appointment alone or dealing with finances, I had to step in. My sister is an hour and a half away, so it was easier for me to take a few hours for a doctors appointment. When something happened in the middle of the night, I was the one to head over to mom's.
There were things that she could do from a distance, though. When we needed to research hospice and care homes, she ran point. When mom was in the hospital various times, my sister would come up and spend the night with her. She was the contact for care home administrators, hospice people, social workers, etc. If something wasn't going right in those areas, she'd make the call - she has a knack for getting cell phone numbers and always had a direct line. I spend more time dealing with mom and her affairs, but my sister was great and extremely helpful to me and my mom.
For those going through these issues now or will be going through them soon, I suggest trying to find roles for more than just one person. All of the financial stuff can be done online now, many medical things are online as well. My heart goes out to those going through the struggle of assisting aging parents.