I've been re-reading the series recently, so the characters have been on my mind. This is a spin-off from a throwaway line at the beginning of the fic I've been writing for shimotsuki since 2012 (which will be finished, I promise - I like it too much to abandon it and I think I've done the hardest bits anyway).
Summary: “It feels like the first day I saw the river, but twice over.”
As it happened, Whit and the baby arrived at the same time.
Both had been expected “any day now” for weeks: Whit off the Trace; the baby in the usual way. The pack train was within groundsense range as Berry’s labour hit the crucial stage and a blurted, “Tell him to hurry up!” dispatched a messenger up the road. In the final throes, Fawn was sent from the bedside to ruthlessly strip Whit of coat and bags and boots and push him upstairs. He stumbled through the door in time to receive a warm armful of newly swaddled baby.
He gazed, wide-eyed, down at the bundle, and then at his wife. “It feels like the first day I saw the river, but twice over.”
Also posted here on AO3.