Back to the Tyger, Tyger poem. In simple terms, this poem begs two questions:

-Who created Red John? ie: someone by some intention drove RJ to be the person they are (on-purpose, not on accident)
-What was their motive in doing so?

People, someone made RJ into the person they are. Shaped and molded RJ, with reason.

After thinking about this, I'm inclined to believe it was from some form of abuse.

Theories:

Lisbon's other, un-named brother, by her abusive and deceased (suicide) father

Bret Stile's son, by his father's own will