My theory is kinda far fetched. I mean there is a high possibility that it's not right. But what if RJ is not just one person? What if it's a group. A group of people which each of them are best at something. Maybe Timothy Carter was one of them and after he got killed others continued their way.
Think about it: Bret Stiles is best at manipulating people so he gets people to work for them. Ray Haffner is good with technology. And I think there's an anonymous person who actually wants to hurt PJ. A person who knows about him. He who maybe has a hate in heart for him for a long time. He is the one that kills people in his own special manner. And he is the one that killed Jane's wife and daughter.
Have you read or watched Agatha Christie's: Murder on the Orient Express? don't you think there's a slight possibility that there's not one murderer but a group of them? a group which can turn people. Which can kill people. Which has been described as gentle and kind also as a beast and animal.
You may ask"Then why people who know RJ talk about him as one person?" well, probably the answer is: Because for each of them only one of them is Red John.
I know it's not what you think or what you find possible but if you were kind enough to think about and comment you would make me really happy.
Thanks for reading,
S.H