It's so hard. With my mother, she kinda deteriorated all at once. She was always different and had struggles, but when she wasn't bathing and we could smell her for miles and she was insistent the neighbours were watching her through a hole in the bathroom, I knew it was time for professional intervention.

PS, I also have a brother, 15 years my senior and our only conversations were about what to do with mom, especially from him to me because he lived closer and honestly didn't want to deal with it.