Character Analysis
Prince Justin appears in Howl's Moving Castle even less than the Wizard Suliman does. Even before Sophie's enchantment, the narrator reports "a new piece of gossip [that] came into the shop. The King had quarreled with his own brother, Prince Justin, it was said, and the Prince had gone into exile" (1.40). Of course, as we find out later, Prince Justin's disappearance comes about thanks to the Witch of the Waste. And the King hires Howl to find out what she has done with him.
When we find out what the Witch has done with Prince Justin, it's a little gruesome. She has put together a body without a head from parts she has collected magically from Prince Justin and the Wizard Suliman. With the leftover parts she has formed Percival, and he has the dubious honor of wearing Prince Justin's head.
When Prince Justin reappears after Miss Angorian's death, his main thought is to go and see his brother, the King. So the fight that initially separated them has apparently been forgotten.