In my humble opinion. Red John is Kirkland and Kirkland knows Patrick Jane from childhood, and I found this hint both given by Patrick Jane's life and Bob Kirkland's chat with Theresa Lisbon.

When Lisbon and Kirkland had their chat, although very elusive Kirkland stated that he moved with his familly on various locations and for that reason he likes to tell that he was "raised in the USA".

Patrick Janes comes from a familly of "Irish Travellers" aslo called "tinkers". Kevin Corrigan (Robert Kirkland) having this Irish background, the connection between the actor's background and Bob Kirkland/Red John seems very likely.