That was news.
Katara tried not to sound too concerned, but couldn't help it. "Why not? Do you have to marry an air bender?"
Zuko looked very uncomfortable.
"No, it's not that," Aang explained. "The Air Nomads don't get married. We're one big family. No one would tie themselves down to just one person forever. That would be selfish."
"Selfish!" Katara ranted. "How can you say that? What about love? What about children?"
"Love is great," Aang replied with shiny innocence. "We fall in love all the time. Children are a gift of love. That's why everyone raises the children together. Some people stay together for a long time and have more than one child, and others share their love everywhere when they travel between temples."
He looked around, and misunderstood the group's expressions. So he continued with even greater conviction, "Everyone should have children with more than one person, because variety is beautiful. And everyone should take care of children. Even monks who have freed themselves from the weight of earthly ties have a duty to teach children."
Suki smirked. Sokka was bug-eyed. Zuko was blushing redder than his nation's flag, and Katara froze in horror.
This was followed by a moment of sparking glances, embarrassed smiles, wiggling eyebrows, and pure puzzlement. Then Sokka's voice squeaked, "So, Aang. Um, how old do you have to be before you, um, give all the lucky ladies children?"
Aang was glad Sokka understood, and answered quickly, "We get lots of practice whenever we feel ready, and then it just happens."
You could have heard a monkey-feather fall.
Then there was a rumble of crumbling earth.
Toph shouted out to the group, "Hey, Twinkle-Toes! After we bury Sparky's father, can I be adopted as an Air Nomad?"