Sibling difference of opinion on mum

My elderly mother, she’s nearly 80 has always been very independent still drives and before COVID volunteered at a local hospice, she was a nurse her whole working life. She looked after my stepfather who had Parkinson’s until his death 5 years ago. I live a couple of hours away and my brother lives 20 minutes away. My brother is dealing with his mother in law who has dementia with his wife which is difficult at times. The problem is that he has started to see our mum as needing more support, which I disagree with. I speak to her via FaceTime daily, I’ve seen her once since covid which went against the rules for Mother’s Day. My brother wanted me to visit at the peek of the pandemic and due to my heart issues I said it was too risky, he didn’t like it. Before my step dad died he hardly saw my mum, I helped steer them with financial matters, and we had family holidays with my parents and my children once or twice year. Once he died my brother took over the financial matters and I’ve let him do this as my mum seems happy with it. He has a holiday home abroad and my mum is expected to look after their dog when he’s away, which was at least 6 times a year before covid. He also leaves their dog with her if they have to go off to do something. She is even asked to visit his mother in law for a cuppa and chat if they can’t do it. Yet he feels she needs more help and wants to discuss this with me,I feel we should discuss this both with mum and not behind her back. Recently she had to see a specialist and may need a small operation. Mum told me about this but I was not to tell my brother, which I respected. My brother then found out and was livid, and said we should not have any secrets. I asked him to ask mum why she didn’t want to tell him. I don’t want to fallout with my sibling but we disagree with what support my mum needs and it’s making me feel guiltily for not being there for her. He seems to be worrying unduly putting in a video door bell and saying that we can put cameras up when needed. I’m not sure how to handle this other than what I’ve already been doing?