These other four wolves are the pups of the pack (besides Kapu, of course). Sister is seen playing with her brother Kapu, but beyond that she doesn't have much of a personality. As for the others, well, Miyax sums it up best when she says early on that they "had little personality as yet" (1.112). In fact, they don't have much of a personality throughout the novel, but that's okay. They're meant to fill out the pack and provide Kapu with playmates. Works for us.