Uh...... If you mean Kaiza, he's not Akiko's brother. He's one of the twists in this story but they're not related in anyway possible. Akiko will encounter other dragons in her journey. Zuko & Akiko will fall in love but it's a slow burn. Like they both just figured out that they're attracted to one another, it'll be awhile until they figure out it's love that they are feeling. I'm open to answering any more questions, so long as they are not to spoil the story.
ヾ(˶ᵔ ᗜ ᵔ˶)