That’s some huge assumptions.
of course I personally want to help when someone is distressed. However, working on the assumption because some feels they can’t, they must be selfish comes from quite a privileged position.
You weren’t the only support in the entire world for your mother. You had, at least (probably more) one other person to carry the load. So even if you found your mum distressed, your mothers emotional well being wasn’t only on your shoulders.
If a person needs a break because they are also going through a difficult time and are always the only support person available for a parent there is nothing? Inherently selfish, about needing a break yourself. We don’t know enough detail to making sweeping statements like he doesn’t care, he is offering no support or that you were a better child to your parent.
You don’t need to have been in the same situation to get that one, barely adult, has a high chance of struggling being his parents only emotional support and grieving himself and may need a break himself, for his own mental health. So he can support her again today or tomorrow.
You aren’t in the same situation and we don’t have the detail to decide wether you were a better child. Or a better person or that he is being selfish.
Not everyone can give constant at emotional support for days on end? With no breaks and mother person to carry the load with. Especially, when they are grieving too.