I was in exactly the same position. After my father died my mum was fine for a few years . Mother had always been a difficult person, sarcastic and not social, well able to drain the joy from any visit. I visited her at least weekly, a 40 minutes drive. I was working full time.
She gradually became more gentle natured and easier to visit. Despite having a brother who lived closer it fell to me to sort the large garden, cut hedges etc. Sometimes I got a man to do some heavier work.
Then it became clear that all was not well. Again I dealt with doc and eventually a crisis when I was not there convinced doc that an assessment was needed. Alzheimer's had come to visit.
A home package was put in place for which I was grateful despite it being woefully inadequate. I took all washing and ironing, did a food shop, not a lot as I'd also arranged meals on wheels, and cleaned the few rooms that she used. Brother visited mum at random taking a newspaper with him. But did no chores.
A few years I organised a care home 5 minutes walk from my home, brother was kept in the loop but didn't make any effort to help with the process. 2 months after entering the care home mum died. Brother did help greatly with the funeral arrangements.
I organised the house sale, the solicitor, the Will arrangements and eventually brother got his due half.
Something I got fed up with db but didn't fall out with him, he was always like that, his own home and garden were always in the midst of a job being done the was never completed.
We are good friends, mother had been difficult and at times especially sharp tongued with db wife who didn't deserve it. Alas, mother reaped what she sowed in that situation.
My brother is still woolly headed, he is also one of the kindest people I know. But, when it came to coping with mum I just knew I was on my own.