First of all, I'm sorry to hear about your brother, if I could fathom that sort of experience I would offer a bit more in condolence, but I don't so I'm at least glad you have resolved the impacts of that in yourself.
Yes, it can be painful losing a friend or relative, but it's natural and inevitable.
This is very, deeply, painfully true. However, just like your parents I don't believe any conscientious parent would want to expose their child-- doesn't even matter how young-- to a loss like death be it in the family or not. Your parents made an understandable and well-meaning decision to shelter you from the event of your brother's death. They could not foresee the consequences on you or how you would try to make sense of it in a mature way, moreover how trying to do so would impact you personally over time.
I don't think I would let my kid see someone die. I also wouldn't forgive myself if I justified letting him stay at a death watch as some sort of lesson for life or manliness. There are some headstrong, intelligent, and wise adults I know that came from various parts of the Middle East as actual child refugees, of war and poverty and the like. Some of them experienced death close-up and first-hand. They all claim it stayed with them forever and is a strong internal guide, an invaluable experience in the end. None of them felt it was something they would want anyone else to experience.