My best friend's son is dying of cancer and it's breaking my heart

my best friend's youngest son who's only 10 is dying from a very aggressive brain cancer and I'm absolutely devastated.

I've been my friend's shoulder to cry on throughout this whole thing and I can't handle it anymore, I've been there for both of my friends parents deaths and even his little sisters death and nothing has destroyed him like this, the kid is deteriorating more and more every day and there's nothing they can do about it, my friend is one of those tough guys who never cried in front of anyone before so everytime he cries to me it's like pulling my heart out.

he's the youngest out of my friend's 5 kids so it's so much worse. not that anyone else getting it would be better but you know.

yesterday was the worst, the kid was in so much pain and we were all there with him in the hospital and my friend just broke down in front of his wife and kids and I had to comfort him again, it's killing me.