I strongly disagree with that attitude that one-upping a sibling or other relation is more important than retaining a sense of humanity and fairness, because, in the final analysis, that is what you are attempting to justify.
I'm glad to say that I donated platelets to give several years of life to a family member who I'm sure had done more to damage me in the past than this guy could have done to his sister, assuming he did anything significant in fact.
I don't know why many people think it's so desirable to wind up with the 'biggest asshole' trophy, particularly at the cost of others' lives.