Between Kris and Bruce there are 10 children. Kris and Bruce each had 4 children with other people before they had Kendall and Kylie. During the special on Kim and Kris' marriage you see him with the four oldest toward the end.
I admit that they are a guilty pleasure for me. I don't know why I find them interesting as I would agree with most of the criticisms in this thread, but I do find them oddly fascinating. I do think that they have a good work ethic.