Why does it seem like the Kardashians aren't close with their stepbrother Brody Jenner?

I mean the Kardashian's mom (Kris) married Bruce Jenner when they were little kids. Bruce had 4 kids and the 8 step-siblings all grew up together practically. They all share half-sisters Kylie and Kendall. Why is Brody barely mentioned on their show when he's already famous? And the Kardashians weren't ever spoken of on the Hills either. There's never any pictures/video of them hanging out and Brody didn't even go to Khloe's wedding. I can't imagine them being friends, let alone siblings.