"Bumi, what?" Tenzin finally choked out. "How?"
His brother was pacing up and down the ship's small room. "You want the full story? Alright," Bumi said, running his fingers through his wild hair. "You know that as a commander in the Forces, I've travelled to everywhere and anywhere, which includes small port villages in the Earth Kingdom. And around seventeen years ago, I met a woman in one of those villages. The most interesting woman I'd ever had the fortune to meet. Suna."
"Is she-?"
"Dead? Yes." Bumi nodded, continuing on with his story. "Even though we were both adults, we both still had our rebellious streaks in us. She, as the eldest child raised to always be a role model for her siblings, and me, the Avatar's son, both wanted to break the rules. Do what wasn't was expected of us. So despite me always on the move in the United Forces, we got married. And whenever I got the chance to visit her village, I did."
"I do not want here my conception story," Ling said, shocking her aunt and uncle. "Sorry," she said a moment later, her head hanging down.
Bumi grinned. "I can see the Suna in her. Anyway, during the crisis with the people of Ba Sing See attempting to secede from the Earth Kingdom, I didn't get to see her for months. Almost a year. And I couldn't ask for a transfer down to where she was, since, well, nobody knew about us." He sighed. "Biggest mistake of my life. Believe me, I wrote to her as often as I could. But after a while, the replies stopped coming. So the moment everything calmed down, I went down to her village. But Suna, she wasn't there."
Pema's hand flew to cover her mouth, and Tenzin stood frozen in shock. His mind was reeling- how could his only brother have a wife and daughter that nobody knew about?
Bumi swallowed, and carried on with the rest of his explanation. "At her family's home, there was a baby. Suna had died not long after giving birth, and they hated me for it. They blamed me for turning their daughter wild and then killing her. They told me to stay away from them."
"Did Mom know?" Tenzin asked quietly.
His brother nodded. "I told her everything as soon as I could get from the Earth Kingdom to the South Pole. She was the only person to know the whole story. But she told me it was ultimately my decision on whether to fight for Ling or let them raise her."
"Bumi, you know that we could have- would have- helped you with her if we knew," Tenzin said. He knew that Bumi couldn't have just abandoned his role as Commander to raise a child that nobody knew about. Even under normal circumstances, a scandal would arise. But when it involved the Avatar's son? Unthinkable.
"I know. But I had robbed her family of their eldest child, and taking away another would feel even more criminal. I had asked if I could visit, and they said no. But whenever I could, I would visit the forest behind their home- stealth is a skill they teach in the army, and I passed that exam with flying colors. Anyway, I would sit there and wait for a glimpse of a black-haired little girl running around. Until one day, I ran into that little girl in the woods."
Ling stood up from the cot she had been sitting on. "I wasn't running away, not really," she defended herself. "Grandfather had been yelling, and I knew that he was stressed because Grandmother had been sick, but I needed to get out of the house. Breathe a little."
Her father laughed. "And breathe she did! Exactly the way you and Dad used to, I noticed. Sit silently and gently pull the air around you."
"So you're… you're an airbender?" Pema finally asked Ling.
She nodded. "Nobody had told me who my father was, or that I had airbender heritage. And when I discovered my bending, I didn't tell anyone. Everybody thought that the only airbenders left in the world lived in Republic City. Of course, I didn't know that I was related to them."
"And after I was done hiding there with my jaw wide opened, I finally approached her," Bumi said. "Ling, of course, nearly screamed for help since there was a strange man in the woods was trying to talk to her. But I was quick enough to introduce myself as her father."
"It's been a long three days," Ling said with a sigh.
"Once I was able to convince her that we were related- the fact that our ears are identically large helped- I told her that my family is chock full of airbenders. I could tell that relived her. She took me back to her family's house, and her aunt immediately recognized me. But after Ling calmed them down and revealed her bending to them, they realized that keeping her in the village wasn't the best idea."
"I love them, believe me, I really do," Ling began. "And I know they love me. But we're hardly related to any earthbenders, let alone airbenders. They didn't know what to think of me when I showed them what I could do."
Tenzin was still processing all of this new information. Bumi had a daughter- his niece- that nobody had known about. He'd been widowed with nobody to turn to for comfort.
"Ling, do you want to be taught airbending?" he finally said.
Ling nodded, her eyes meeting her uncle's. "That's what I've wanted ever since I was a confused little kid, and ever since Bumi- sorry, my dad- told me, it's finally sinking in that I'll finally know how to properly bend."
By this time, the light from the now rising sun had begun to pour into the below deck where they had been assembled.
"The kids will be waking up soon," Pema told them. "Let's let them meet their cousin."
Hey, so this was written before the premiere of Book 3 or 4, which is why there aren't any other airbenders around besides Aang's descendants. Which makes it a bigger deal that Ling's an airbender.