Okay, so these four are the youngest children in Fai's family. From left to right, Kana, Sari, Eri, and Tara. Eri and Tara are twins, but Tara is the more playful one. Eri is more the "voice of reason" half of the pair. Kana and Sari are both earth-benders like Fai. The twins are non-benders like Lima.
Characters (c) ~Ximona Legend of Korra (c) Mike and Brian