Brother taking advantage of parents financially under guise of caregiver

So my brother has pretty much lived with my parents for the past 10 years; after graduating college (which my parents financed) he was never matured to be fiscally responsible, eventually got evicted, car repossessed, etc, and became homeless. He moved back home because of course my parents wouldn’t let him be homeless and starve. They helped finance his life without charging rent him (food, co-signing for vehicles, traveling, etc). Prior to the pandemic, he was working, but was still heavily relying upon my parents for living expenses and recreational things.

As my parents can help whomever they wish, the larger issue is due to the fact that they have now been living in consistent debt secondary to maintaining my brothers existence. Furthermore, he has stopped working since and my parents have become even more dependent upon his assistance due to health issues (my father is basically non-ambulatory due to sever arthritis and my mother was recently diagnosed with a mild form of dementia). At this point, my brother is fully responsible for their transportation to doctor appointments, shopping, cooking, cleaning, and monitoring my mother given her stage of dementia.

However, even while it’s now very much undeniable that my parents need significant assistance, their financial situation continues to worsen given their rising healthcare and medication cost in addition to the non-essential spending of my brother.

These days, my father, who is in main control of their finances, cannot refuse my brother when unreasonable request, such as traveling for his birthday, unnecessary clothes shopping, etc. My uncle and I have tried to speak with my father about restricting his income from my brother, and he responds with “if he wasn’t here, I’d have to pay someone for help anyways”. And I genuinely feel that my father has gotten so dependent upon my brother that he truly doesn’t want him to leave or find a job at this point.

While I wasn’t able to contribute physically like my brother or financially for the past several years due to completing school, I have now started my first job. However. I do not know how to assist in a meaningful way as any money I provide to my father will certainly be mismanaged by my brother. He has total access to their banks accounts and cards. I am certain that my brother will play the “you weren’t here card” if I try to exert any authority over situation. I do not wish to attack my brother and make him feel like his contribution was meaningless, because homeless or not, he has certainly played a vital role in keeping my parents somewhat afloat. However, I do not see how additional income will provide any benefit if they do not get their spending under control.

I have thought about taking on my parents mortgage or medical bills myself, but this will surely just been seen as freeing up money for more frivolous spending. I have thought about putting a monetary value on my brother’s work and allowing him a reasonable salary, but that would be very expensive and they aren’t truly a licensed caregiver - if going that route, I would much rather hire someone truly trained and competent in the field.

I’m stuck between a rock and a hard place. How do I get my parents financially secure, physically taken care of, without my brother feeling under-minded?