Red John is patrick janes dad. He is stubborn, easily could be violent, felt betrayed by Patrick and jealous that his son made it so famous and left him as a side show circus act. Also Patrick belittled red John and this caused his dad to snap and kill Patrick's family. He feels there is a point to prove that he is smarter than Patrick and is all the time teasing and leading Patrick on this huge chase. It is all revenge from a jealous hateful father. Also his dad has said to him 'he always follows things through to the end' , and in the episode'throwing fire' he tells young Patrick he is off to play poker with the boys!
This is the poker meetings where Lisbon and the high ranked cbi go to play.
His dad has worked his way to the top and has connections everywhere. He has the abilities that Patrick has and has used them to become powerful and feared.

Done!

Hi Guys, 

Honestly, I have still no idear who Red John is. Although I have some theories. I believe that it isn't Jane or any of his team, (meaning Lisbon, Grace, Rigsby or Cho)

What do I believe?
I believe that Theressa has met Red John at here pokergames with Bethram. I also believe that Bethram knows Red John (not being aware of it) and that they met in that Pokerclub of theirs. Same place where Theresa met Red John. 

Here's my theory about RJ. I am damn sure that RJ is going to be PJ himself or PJ's brother.  
 
1. Their voice is similar. Watch this:
http://www.youtube.com/watch?v=OUikVzxQuuY
 
2. Red john smiley resembles with PJ's face.  
 
3. Morale behind 'Tiger Tiger burning bright' poem as said by Cho in Season 3 last episode: Good thing can't exist alone. You can't have life without darkness.
 
"Tiger, tiger, burning bright In the forests of the night, What immortal hand or eye Could frame thy fearful symmetry?"
 
Hence, words "tiger tiger" or "symmetry" suggest that RJ can be the dark side of PJ or it can be PJ's brother of almost same age, same intelligence, same psychic nature but having darker side.
 
Hence, RJ is either PJ having a hidden dark side or someone like his brother who is as clever as PJ but has dark side associated with him.
 
But as Lorelie said, they have shaken hands. As one cannot shook hand with himself, I think its gonna be PJ's brother.

Great episode and final scene the other night. I know all the RK accusers will think it proves it's their guy but I'm not so sure! I did think when he showed up his story line was going to take a different direction altogether so I was surprised he killed the guy. However Lennon worked for RJ (he brought LMs sister to him) so for RK to be RJ you wold have had to take the plastic surgery route away the whole do you recognized me speech. That's fun and all but your gonna tell me that between the time RJ and Lennon worked together, a few years ago, this guy got plastic surgery and still rose to the level of homeland security position??? If Lennon knew him as RJ he woulda freaked out right there.

Hey it's tv so who knows but what I've taken away form RK showing up is mainly in the last two episodes,,
1) his little conversation with Bertram about trusting Lisbon. This still says to me they (Bertram prob unknowingly, cause he's not to bright) are protecting somebody higher, a judge or AG. And
2) when he says "I'm a friend" to Lennon. Remember when Stiles told PJ where Christina was hidden? He told PJ to consider it a gift from "a friend". So this friend is either RK's strange personal moniker or it's how people that do RJs bidding code themselves. Like the mafia uses "friend of ours"

RK is clearly on PJs radar now and that's gonna be the trail till the seasons end. With at least the next 2 years pick up and the actor just being a guest star you not going to get the RK is RJ bow tied up real quick......then again I to tv!!

Stop with all the crazy elaborated theories!!!
Face change or transplant, c'mon.

Think of Bruce Willis in Sixth Sense.
The best solutions are the simple ones, the ones who happen to be right under our noses the whole time.

My guesses are Bret S. or Brett P. but who knows... well Bruno does.

I think whoever Red john is, he is very close to patrick or may be his relative. Because Red John has killed everyone who tries to find him. Then why not kill patrick?

lets face the facts, everyone who joins late in a series and is involved quite heavily with the CBI is usually red Johns man I.E O'laughlin or Bosco's assistant, it would only make sense if Kirkland was a Red john accomplice, i have a strong feeling RJ will kill him once PJ gets closer.