That's my niece and nephew, Joey and Meital. Joey is six, and Meital is four. For two siblings close in age they get along smurfingly well.
One evening while sitting in my sister's home, Joey sat at the table, saying: "You know what? Meital is stupid." And Meital said, "I'm not stupid. You're stupid." And Joey said, "No. Meital is stupid, because she farts a lot." As this kind of discourse went on, my sister said, "That's how I know Joey is tired. When he is mean to Meital. Because otherwise, he would never be mean to her." Which is a pretty good deal, I have to say. And, anyway, you can;t get too mad at someone who looks like this: