Striking resemblance

[Spoiler Warning, for those of you who haven't read these books and are planning to, are advised to read this afterward]

I've been wanting to write about this ever since I finished reading Dan Brown's Digital Fortress. I'm not sure whether other readers notice it or not, I've tried googling but no one seems to share the same thoughts. I've read all four of his books and I like them. Well, not sure how to say it (I'm not a reviewer :-), I enjoy reading his novel, the story goes how I want it to. The good guys always wins and the bad guys got it bad (which probably the standard plot formula of all times for both movies and novel he he..). However, there's this characterization similarity that I began to notice after I read three books. The first one I read was The Da Vinci Code, which I have to admit, it was because all the hip and hype about it (pretty much based on the controversy of the book). Then I read Angels and Demons, which actually Langdon's first adventure. Do you see the similarity between these two books?
The antagonist in The Da Vinci Code, Leigh Teabing a.k.a The Teacher, Langdon obviously trusted this guy since he decided to come to Leigh's château when the police were on their tails, but later in the story as the plot advanced, Leigh was behind Aringarosa and Silas. He was the one who controlled them.
In Angels and Demons, Carlo Ventresca a.k.a Camerlengo a.k.a Janus, he seemed to be the good guy at the beginning of the story, he assisted Langdon in their search. But in the end, he turned out to be the evil mind.
So, come to the next two books. Deception Point and Digital Fortress.
In Deception Point, William Pickering, Director of NRA, a.k.a The Controller, one person that Rachel Sexton really believes, he actually was the one behind all the killings and as a matter of fact, was the one who finally ordered to have Rachel eliminated.
And finally in Digital Fortress, Commander Trevor Strathmore: Deputy Director of the NSA, head of Crypto, who was secretly in love with Susan Fletcher, and the one who seemed to be the hero, was the one behind all the manipulation and fiasco.
And you know what, all main antagonists, all of them had means or accomplice. In Angels and Demon there was the Hassassin. The Da Vinci Code was Silas, Deception Point has the Delta Force team, and Digital Fortress has Hulohot as the assassin.
I'm currently waiting for Dan Brown's fifth book, The Solomon Key. I am wondering, how the plot would end up.
Mmm, what do you think guys?