I want to add, that you can actually call your county's department of human services (DHS) and start the process for a county assessment of your sibling. First, you speak to a social worker on the phone. Describe your sibling's behavior changes and how you have taken on the caregiver role since your sibling is not capable of independent living. The county can set up a date and time with you to come out to your house to assess your sibling, and determine if they qualify for county support. That means, you could move your sibling into a nursing home memory care unit with the elderly waiver or equivalent (state by state call it something different I think).

So, you are not alone here. You have access to help. If you are afraid of being judged by the doctor's office or county assessor, don't be. Part of their job requires them to interview the caregiver (you, in this case) to find out what tasks and responsibilities you've had to take on to help your sibling live day to day. The county can also do a memory test on your sibling to determine the onset of dementia.