Should I allow my Brother and Sister-in-law into my home where Mum lives? It's a decision that I never thought it would come to.

Four years ago my Mother - who is 93 and has no money of her own - lived with my Brother and his family. She helped raise their two children - as one is a workaholic and the other had a full-time job. Five years ago she began announcing that she was "becoming stupid" and not to count on her for anything. My sister and I would come in from out of town and take her out and shop for her and a local person would clear her apartment in my Brothers house. It slowly became clear that she could not cope and she was sleeping more and more and the clutter increased. Many times she did not know if it was day or night - and was just watching CNN for most of her waking hours. It was increasingly difficult to motivate her to take walks and stay healthy. She was eating porridge morning and night and seemed not to be able to handle anything mechanical. About that time I invited Mum out to my place - a small cottage on a farm that I was renting. I then saw how many small things Mum needed help with - just to bring ease and to reduce her confusion. I was working from home some of the time and Mum now used her energy to go for walks and we went on many "soft" adventures. Every time she'd return to my Brothers she'd cry and believe she would not be coming back - and for the first few times I believed it - even though in the weeks or month she was with me she'd recovered some strength - she was still fragile and it was heartbreaking. Often from the first day Mum came to visit me - my brother would be calling and telling Mum that she must return and quite honestly he used guilt - I think he believed he was making Mum feel wanted but over the coming years he played the guilt, and the "do you love the other son," more card often.
Now here's the kicker. He's a scientist / medical doctor and world famous, he'd taken over all the decisions for Mum's physical health - and he maintained till five weeks ago that Mum had no care needs and he has never arranged a visit to a geriatric specialist. Only other specialists that he knew at the hospital - very frequently - whenever he wanted Mum to come down - we'd drive all the way into the city - really at his whim - or to ally some of his concerns - to the hospital where he works.
Over the past five years Mum has come to live here full time - she is now completely open and straight forward about where she wants to be and won't be manipulated into anything anymore.
Recently he scheduled an MRI for Mum against her wishes - she has claustrophobia from her childhood of being pushed into a drying oven in the convent she was sent to as a child. He was also talking about her having other invasive techniques - so both Mum and I agreed enough was enough and I finally called the local geriatric outreach program and they outlined a strategy that involved a geriatric team assessment including OT and Social workers from a few agencies - a local Family doctor to coordinate this - as well as secure all Mum's medical information in one place. So this process is nearly complete - and what has emerged is that Mum has received exceptional care - and is in wonderful spirits and health - that her dementia is moderate to severe and that she requires full time care.
However, I know this is long, just trying to give a full background as I've really appreciated the advice I've had here before - but I've exhausted my resources - I'm renting this house - I've compromised my business in caring for my Mum full time for a while, also my relationship - who was helping care for my Mum - could not take the full-time nature of it. So I'm making a work transition - and have to find a way again to earn a living from home - have no savings as I have been doing all this for 4 years without any family acknowledgment or support.
There is some evidence - that my brothers strategy is to let me sink and rescue Mum - then have her back at his house - and then I suppose he could pay the house cleaner to provide additional care for my Mum - or hire someone else - as he has ample money for this.
He's now after all these years - made an appointment with the geriatric specialist and booked it for this Friday - there's no waiting for appointments - but it also in not part of any care strategy.
The problem is I have tried to think of every possible reason why they have not supported Mum's living her, or acknowledged her care needs - or had a diagnosis, and now when I've been up front and sent detailed emails - I get NO response. Except a $2000 etransfer that I could not take without any discussion or understanding - no matter how much I needed. And it came with the message that it was so Mum would not be so worried. I now feel they are actively pursuing a strategy to bring Mum to their home against her VERY clear wishes - that she has said literally 1000's of times. And Mum has stayed very lovely as she has been cared for - and now they want that loveliness for themselves. Do I let my brother take Mum to see "his" geriatric specialist?