Here's Katara's bit. Fair warning, these get progressively shorter as they go on. Anyways, the inspiration for this actually came from my story "Sing" about Mako; I figured Katara would do the same thing. Here go.
The world fell apart when Katara was six. Screaming and crying and trying to convince everybody that Mom was not dead, she was just sleeping, she would wake up but only if they didn't put the coffin in the ground, she experienced pain like no child should. She and Sokka comforted each other at night and fell asleep curled up underneath a giant quilt on the couch more nights that she could count. It shouldn't have been like that, it should have been their father comforting them, but it wasn't. His job had always made him travel, going on long business trips to faraway places, and after Kya's death he was gone even more.
Katara didn't tell anyone, but she knew why he left. She saw the way he looked at her, grief and pain and angerin his eyes. She looked like her mother.
Gram Gram tried her best, but she couldn't be a mother and father to them, and as Katara grew older, she clung to the one thing she had from her mother besides an old necklace: Her songs. Mom's voice singing a lullaby as a ghostly hand brushed Katara's hair, Mom's voice singing folk songs while she waltzed around the kitchen with her daughter on her hip, Mom's voice singing along to the radio and interrupted when a car smashed into theirs.
Katara's voice trying to mimic her mother's.
She felt close to her Mom when she was singing the familiar old tunes, clutching her necklace. She kept the singing to herself, hiding in her room and clutching the necklace and crying. Her father entered her bedroom one day while she was singing; she stopped and stared at him.
"We might as well get you some proper lessons," he said, staring at the floor. She gasped in amazement. Proper lessons? He was going to get her a voice teacher? "You sound like your mother." Her heart sank, but then he added gently, "You have a very nice voice, Katara."
She almost cried she was so happy. Her teacher was amazing; stern and unbending but caring. He taught her everything she knew.
When she was twelve she started writing songs, letting out all the grief and anger she could express no other way. And when she was twenty-four and found herself suddenly the lead singer of a band, it was her music that they played and her words that they sang and the pain she felt at her mother's death and the anger at her father's semi-abandonment faded away.
And she loved it.