In either case, please let 'him' know that there is atleast another human I know - who empathizes with your 'friend's' situation - someone who's been through somewhat similar stuff when her father was on the death bed - her self-sacrifice was also in vain and caused resentment against her siblings-with-excuses. However, she wisened up and acted practically when it came to her mother's demise. She wishes to recommend 'your friend' a movie[0] that captured some of the petty sibling problems that you may find relatable (won't solve it but then - Some problems are unsolvable). Also, it translated well from a local theatrical play into an AV medium with sharp & insightful dialogues.
[0]Family Katta: https://www.primevideo.com/detail/0R9TTKN7U0DGT1L141HP48N76N
Even here you have to be careful.
True Story:
He had "made it" in the US with a "Green Card" and a promising future. His elderly parents were living by themselves in his home country and suddenly his Father passed away. Within a year he had to make a judgement call on whether to get back home to take care of his Mother (an ailing, helpless and needy woman) or continue with his life in the US. Filial piety, Affection and Love for his Mother made him choose the former option. The result? His job and career gone with an abandoned "Green Card" and nonexistent future. He has ended up as the sole caretaker and caregiver (living off of his savings) for almost a decade now. This is now the "norm" and the expectation is that he would continue doing it until the Mother's (or his) end. He is frustrated, angry with everybody (especially with his siblings) and is basically trapped for the foreseeable future.
So what did his self-sacrifice gain him? An emotional decision cost him everything.