The sibling you see in this strip is Keri, a twelve-year-old who follows Sasha's example in everything. (Yes, you may now shudder.) She's a lot more aggressive than Sasha, however, so when Sasha gets mad, Keri's the first person to goad her into taking it out on something. Janice is nine years old and a lot more level-headed, but she also tends to follow her older siblings, so it's common for Keri to talk her into some ill-conceived scheme. Hopefully "susceptibility to persuasion" is a trait Janice will outgrow.