To my mind, it's a matter of priorities, and this was what surprised and disappointed me about my invisible bro.
I know he did love our little Mum and doubtless found it hard to deal with her diagnosis, but she wasn't so much low down on his list of priorities as not on it at all. Granted, he lived an hour-and-a-half's drive away and wasn't in a position to have any practical involvement in the caring side of things, but the one thing he could have done was make a regular commitment to come and spend time with her, maybe ferry her round a bit to local scenes of her earlier life & childhood. (She was unfailingly sweet & never difficult to manage, and I'd never have simply 'left him to it.') But this would have involved setting aside most of one day every 6 weeks or so - one day of his free time that, come the designated day, he might have wanted to use for something else.
So what she got was the odd hour or 45 minutes (an appalled carer told me about that one) maybe twice a year tagged on to a visit up this way when he came to see his friends. Fair dos, he always visited on her birthday.
It was the affront to Mum that hurt me most - that, and knowing that he ran around like a mad thing after his wife's parents. (S-I-L told me after her father's death, straight-faced, that "He couldn't have wished for a better son-in-law." Ooooooh, the temptation......!)
Funny they were both keen to be involved in all the socially-visible stuff, like hospital visiting in her last, short illness, and introducing themselves all round at the funeral, which I'd had to organise single-handed while fielding emails from said S-I-L reminding me "it's important that everyone feels they have a voice in the service."
Sorry about the rant (surprised myself there.) I don't often look back in this spirit, but doing so now only confirms how really dreadful their behaviour was, both by omission and commission.