Red John is not Kirkland's brother.  Some people are saying that the hand shake between Bob Kirkland and PJ was actually with Michael Kirkland (Lorelei has already said that PJ and RJ have shaken hands).  

If that was true then the first time PJ met Bob Kirkland, they would have shaken hands again or at least Bob Kirkland would have introduced himself again but all other times they meet each other its like they already know eachother.

(Same idea also applies for Theresa since Bob has met her many times aswell).