webpack2 creates 2 instances of same version of React

In my project webpack2 is bundling 2 instances of React, and they are the same version. this results in a runtime error. How do i force webpack to pack it only once and make references.

These are my dependencies:

Main Module --> SubModule1 --> SubModule2

Both SubModules depend on React, in this manner:

SubModule1-->React
SubModule2-->React

Both Sub modules have all of their dependencies defined as external, in this manner:

 externals: Object.keys(pkg.dependencies),

I have tried to use commonChunkPlugin, but it didn't help

Can anyone help me understand this, and offer a way to resolve?

Thanks