Two viewer of same scene in VTK

The VTK library really is powerful . The question that I could not handle was how we could just create a scene with 2 cameras! , I found that we should create 2 renderers(from other question/answer), so we should add all objects to both, and if we want to apply any changes to either one , we should duplicate the other one too.

Am I right? How can we prevent duplicating codes(Because it is error prone and really boring.) and just have 2 cameras (two views) in same scene! (C++)