Note: Woo, we got to the 200s now! I gotta say that the version in Project Gutenberg is very concise, cause the textbook I'm using adds a bit more elaboration... Heck, they don't even end this part the same way.
Don Juan receives the blessing from the hermit, and the three brothers go on their way home with the bird. But despite the hermit's advice to not get into any shenanigans on the way home, Don Pedro takes Don Diego aside and tells him that they should kill Don Juan (cause he got the Adarna bird and everything, Don Pedro probably thinks that Don Juan is gonna become even more favored.)
But Don Diego protests a bit and says that it's gonna be a bad thing, that their poor brother will lose their life like that. And so Don Pedro suggests that they just beat the heck out of Don Juan and leave him on the mountain. They agree on it and do it.
The two then take the Adarna bird and went home to the kingdom of Berbania.
The king asks what happened to Don Juan and the two answer that they don't know. Because of that answer, the king gets even more sick. Not only that, but the Adarna bird starts to lose feathers and refuses to sing because Don Juan isn't there. (From how it reads, it seems the king can't believe that the bird the two princes brought back to the kingdom is the Adarna bird simply because it didn't seem like what the healer said it was like.)
I'm guessing jealousy between siblings can't really be eliminated when one is favored over everyone else, so I can understand Don Pedro and Don Diego's thinking and actions.
Still, it's not right, and I'm kind of glad to have it bite them back, but now we've got a king that's more ill and a bird that's lost its rightful owner. Well, I'm guessing that Don Juan had become the owner considering he was the one who captured it.
I'm guessing Don Juan would survive, but would how would he respond to this?