Grace & Peace!
Raster, there is an organization called the Priory of Sion. Or there was, at any rate (Jean Cocteau was its head at one point, if i remember correctly). Whether it still exists is a matter of speculation, I believe. Someone may have more info.
The Priory apparently had something to do with certain conspiracy theories regarding Gnostic legends and the Merovingian bloodline with a bone to pick with the Vatican, believing that the Second Coming would be the restoration of a Merovingian King to a throne in Europe… It makes for fascinating reading, but I don’t think these theories stand up to much scrutiny and remain interesting fantasies. Little more.
Regarding the existence of “secret societies,” such things do exist. Of course, if they really are secret, you will not have heard of them…
By the by, I’ve not read the DaVinci Code and have very little interest in doing so.
Under the Mercy,
Mark
Deo Gratias!