The ironic luxury
For a young child who is forming their assumptions and perceptions of reality, it isn't helpful to spoil them, because they'll get a false sense of security. This time, luxury is a bad thing, because it prevents Henry's father from seeing ways he could actually parent instead of just spoiling his sons and ignoring them. It also corrupts Henry's perception, and it corrupts Franklin's character.
Tragedy as a good thing
Because luxury and pleasure had become something of a cage for young Henry, it's a valuable moment when he is forced to bear witness to life's "dark" side. That doesn't mean that the death of his brother is a good thing, but it does mean that Henry learns from that horrific experience, and that new knowledge frees him from the cage of his father's luxurious support.
The irony of Franklin
Franklin is Henry's hero, but that's partially because Henry doesn't know everything about Franklin. Although Franklin was often a good role model, the unfortunate truth is that he had begun sliding into pretty dangerous character flaws, flaws like racism and bigotry. This happened because he was spoiled, but also because he failed to do the journey that Henry does to honor him. In this way, Henry honors Franklin's legacy by learning from Franklin's mistakes and by making his brother's legacy into a force for the family's ultimate good.
The ironic friend
In light of the suffering Henry endures in the aftermath of the sudden death of his brother (especially since he was so badly spoiled his entire life leading up to the accident), he learns from his friend Sanborn that wealth does limit the depth of a person's character. This helps Henry to understand in what ways his father mis-parented him, namely that his father avoids suffering, so Henry decides to allow suffering to shape his character.
The ironic companion
Things turn from interesting to downright perplexing when Henry realizes that his companion, Chay Chouan, is actually the same man who hit Franklin and killed him. This means that part of Henry's journey is forgiving Chay, which might have happened anyway, but now it has to happen in Chay's literal company, company which is situationally ironic, given Chay's role in Henry's ordeal.
