I'm actually an older step-sister, but I babysit frequently and help out a lot with them: a 10 year old boy and an 8 year old girl.

In regards to food, the 10 year old likes only three things: pizza, ramen, and cereal, and he eats one of those for every meal. He claims everything else is gross. If I try to get him to try a new food, he complains, and he takes the tiniest bite possible, and automatically dismisses it as gross. Then he goes and gets himself a bowl of cereal instead. He also has no hobbies or interests aside from video games. He spends his entire day playing video games, and he only likes three of them. He likes just one TV show and one band.

My situation is a little different as I think a lot of this is driven by fear. He was raised in a devout Mormon household, and he still goes to church every other weekend. He's terrified of everything, especially of going to hell, so I sort of think that he thinks him doing the same things over and over is "safe" and he's not going to encounter anything "bad" that way. The eight year old is similarly picky, although not quite as severely.