Forever Young
He'd gone first; had simply passed away in his sleep one uneventful day.
The world continued to turn with Katara on it and the peace stayed. It seemed that in his death peace was more refined and pushed than ever, to respect what he put his whole life to restore and relive.
The funeral had been bigger than the first post-war celebration of peace and order. With all their children and grand-children, Katara had shaken hands with frail fingers and had tried not to cry so much. She would have just waterbended them away, but Aang seemed to have taken so much of her strength with him.
She continued on, sometimes cursing the longevity that water tribe people held. In that time she watched her children age more and four more grand-children graced the earth. They were beautiful, and there had been a pair of twins. One had had his eyes, the other hers. When she saw their eyes as she helped deliver them, so young and so lively with their cries, she felt herself cry like at the funeral.
Slowly, as she saw the new Avatar rise with all her power and her friends pass away to join her husband, she began to feel more and more alone.
Katara suddenly found herself void of friends she could truly relate to. She kept herself occupied with teaching waterbending and giving inspiration to passing by people, some coming to the South Pole solely to hear her stories of heroics and love. She helped raise her grandchildren with her still-frail hands and wide smiles.
When her own time came, she let her last breath out with relief.
She was finally going to see Aang again.