Sekai

Brother died when they were two months, fell into the river and drowned, add a tragic backstory! Plus her name means, "be humorous," so basically she takes that to heart, copes with humor, over all goofball and tries to make it to where no one notices anything is wrong. But her brother's death actually really hit her hard.

Her brother, Sekani, was the more adventurous of the two. Which proved less than ideal when he went exploring one night. The found him the next day, miles down the river, washed up on the bank. The adults all said he must've drowned. Sekai was only two months old when this happened. Having always been a very lighthearted pup, she suddenly became very morose upon her brother's passing.
She didn't go back to her "humorous" nature until she was a juvenile. Though she felt anything but humorous, Sekani's death still weighing heavy on her. But it was easier to pretend, wasn't it? Than to deal with the concerned gazes of her packmates. It was far easier to joke around, to ease pack tensions, to take nothing seriously so as to run from her grief.