It was a lovely quiet evening. Spirits and humans finally learned to live in peace, the people of Republic City were finally coming to terms with the vines and there were no major threads around. In short: Korra was bored senseless.
Groaning she slumped through the Air Temple Island in urgent search of something to do. As she passed a room she heard something like "Eww" and decided whatever it was, it would do for now.
Tenzin was sitting on the floor with his three oldest kids around him. Meelo was lying on the floor, tongue hanging lifelessly out of his mouth, and his sisters were giggling.
"What are you guys doing", the Avatar asked, as she stood in the doorway.
Tenzin looked somewhat embarrassed as he answered: "I decided the children were old enough to have 'the talk' with." - "The talk", Korra responded questionly. Her mentor looked over to his younglings, then explained: "You know, with the birds and the bees."
Korra nodded knowingly. The way he talked she really should know that one. Sadly, she did not. "Maybe the water tribes don't have 'the talk', because there are no birds and bees at the poles", she suggested to not appear stupid.
Now he was massaging his temples, not a good sign. When he spoke, Tenzin sounded annoyed: "Korra, I mean I want to tell my children where babies come from."
Korra pushed herself into the room with a little "Oh" sound, and flopped down next to Jinora. "You know, that's a really good question", she said, laughing. Tenzin snapped: "I really have no time for this! Just leave us alone and don't make this harder on me than it already is."
As he looked over at Korra, and saw how surprised and hurt she was, it finally dawned on him: "You have no idea, don't you?" The Avatar, master of all four elements (and some more) cheekishly grinned at the small airbenders. Stubbornly, she answered: "Sure I know... I just want to make sure you're telling it right."
Tenzin sighted deeply and started to think. Sure, Korra had been ripped from her home to train with the White Lotus when she was really young. Maybe her parents had forgotten to talk to her. Or maybe they just valued their limited time with their daughter so much, they deliberately didn't tell her, thinking she would find out eventually somehow. In the end, it didn't matter. If she did not know now, he had to tell her.
And so he did.
Some time later Pema called for her family. As she found them, the kids were pale, while Tenzin's face had a little pink blush. She eyed him, questioning him for what had happened. "Birds and bees", he told her exhausted.
He went straight to the dining room, followed by the kids on wobbly feed. Korra was the last, surprising the mother. Looking at the baby in her arms, the Avatar mumbled: "That's disgusting..."