headcannon(?): Jack and Bunnymund know Mother Nature. Not very well, they only know she exists, and they don't know that she's Pitch's daughter or anything about her past life.
When Jack was in terrible condition after years of loneliness she'd watch him and even comfort him as he sat by the trees~ Even when he'd freeze the forests, she'd still be there.
I finally got around to drawing Mother Nature (Seraphina) XD I cannot wait for the new book in september!
Seraphina Pitchiner(Mother Nature)
Jackson Overland Frost
(C) William Joyce/Rise of the Guardians