What are some new pre-teen popstar singers these days?

I mean, it's like I've heard a lot of them but I forget their names and never got a chance to try to listen to some of their music.. I just want to see some of their songs. I've heard of greyson chance and willow smith of course but i know theres more. What are the names of the brother and sister that sings together? I don't know if anyone knows what I'm talking about but they are brother and sister and they sing together or something like that :l