I noticed something after watching season 5 episode 18 where Kirkland killed red john man lennon, after that jane came to him and kirkland called him patrick but in Season 6 episode 4 when jane wants to talk to kirkland in homeland security building, Kirkland called him Jane. 

And sometimes I do feel that kirkland is two different people. at times he seems close with lisbon drinking coffee with her and talk a abit about his past but when he was with betram in his office even lisbon said to him "how could you talk without saying anything" something like that. At that time kirkland seems cold toward lisbon. LIke he never went with lisbon all day finding Jane and lorelei all over california.

So I guess I'm still going with the twin theory. 
Add u to that after seeing the latest episode I have my doubt that one of the remaining 5 is red john. They seems to not have much caliber to be red john to be honest.