Sometimes it is not as simple as one sibling not pulling their weight due to laziness or because they don't care.
My parents are very frail, my DF has dementia, and is physically incapable of getting himself around so is currently in hospital being assessed and given in depth physio in the hope that he will be able to get in and out of his chair when he gets home. He wont be, because he refuses to do anything for himself and thinks he should be looked after and have his every need catered for 24/7 by someone, anyone, else. My DM is also frail and on the surface is uncomplaining and doing her best to get him home. I have 3 siblings all of whom live closer to our DP's than I do, and who (more importantly,) all had a completely different upbringing than I did. Trouble is they don't seem to understand that.
I have cancer and a very compromised immune system. I do not visit hospitals unless I have to for appointments for myself, as I am very vulnerable to infection, I cannot therefore visit my DF whilst he is on the ward. My DM's hygiene in the home is now dreadful, she constantly gets tummy bugs and therefore visiting her presents a different risk, but a risk none the less. I do go there however, but I am very careful about what I touch and never eat/drink anything i haven't prepared myself in a mug I wash before using. I am viewed by my family as being selfish, thoughtless and it has been heavily hinted at that I look OK and haven't had an infection for ages, so am being over the top with the care I take. It occurs to none of them that I stay healthy BECAUSE I take the precautions I do.
Also - and this is more relevant (probably went off at a tangent in the last paragraph but it does serve to show that sometimes, peoples actions are misinterpreted as selfish rather than sensible), my siblings have had a lifetime of completely different parenting to the upbringing I had. I am older than them and have never stood up for myself, just accepted I wasn't to expect fair or loving treatment. I was clothed and fed, but emotionally ignored. This is putting it mildly and in a nutshell, but is the unvarnished truth. Now I am over 60 myself, with cancer, I do not want to structure my life around aged parents who did little to parent me. If my siblings find it hard work and think me unreasonable, then short of telling them how it was (and probably told I imagined it all), there is nothing I can do about that. But I will not spend my own retirement facilitating theirs.