Well they are a family after all so you'd expect some stylistic similarities. If they are close, as they seem to be, then they'd pick up on each other's way of talking, which would be reflected in a quick post online.
And, let's be honest, a quick glance at Twitter, Facebook, Bebo, MSN Messenger or any other internet networking tool demonstrates that there are a number of young (and not so young) people who choose to refrain from using much in the way of grammar and punctuation, therefore making one person's writing style almost indistinguishable from the next!
So glad that Bob has been found! ^