That's not really a frown, but it's supposed to be a casual "If-you-don't-get-out-right-now-I-shall-destroy-you-now" look. You know, the casual look from your casual rogue.
That's basically what I call Rangi and Kuruka. They live in the desert with Kuruka's mate, Baya. There are other rogues there, too, and a pawful of them were left behind by the Outlanders.
Ah x3 Rangi and Kuruka were born in another pride, raised in the Rogue pride (a.k.a the Kubotea pride) and then they ran away to lead their own lives together as sisters.