I know they build a two stage turbo but has anyone ever had built or built a twin two stage turbo?

 

"Stage two" is just a name, there are no set parameters for something to be called a stage two.

There are guys that run 2 massive turbos, for example supra guys. But the majority run a single turbo because you can simplify things with one big turbo.

Have you seen a pair of twins b4, if you haven't they are pretty small. The small one is to eliminate the lag for the second larger one to kick in.