What is required for a human organism to be considered a rights bearer?

[Astonished]

Anyone bring up mental capability? I'm curious about this because I have a friend whose much younger brother is completely mentally debilitated from oxygen deprivation during a swimming accident and is completely dependent upon their parents and expensive medical equipment for absolutely everything. He seems to feel that this sibling's life is a pointless existence and his parents are wasting time and energy that he and his other sibling could have been given growing up if not for the disabled sibling. Recently I learned my foster mother's friend has a full-grown adult son who has been in that same vegetative condition since his late teens (but that guy's loaded and can afford all sorts of extravagances for his son) and I have gotten to have first-hand conversations with him about the experience of being a parent of a fully lifelong dependent 'child' of those extreme special needs, and it didn't sound that bad (granted, that was given that it wasn't outside his ability to afford).

So I've heard good and bad perspectives surrounding this sort of thing. Are there any arguments that differ at all from the standard abortion ones or is it all pretty much the same regardless of what level of mental ability a person has and whether there is any chance of improvement or recovery?