I have two theories

1)In my humble opinion, Red John is Patrick Jane's father. Many will think that is silly, but so far there has been no explanation of what happened to the father of Jane.It makes me feel a director to insert a character in the series so significant and not use it again.Besides, in my opinion, he has several reasons to get back at PJ, after all, as far as we know, his son began to work alone, and if the PC can be a good mentalist, because his father could not.

OR

2)HAHAHAHA, now that is really going to think I'm crazy, but who knows brett stiles is not the father of PJ, after many surgeries, or an old friend of the father of PJ, where the two have started the cult visualize on.
Excuse my English because I'm Brazilian.