Is this what you are looking for?

https://github.com/SharePoint/sp-dev-docs/blob/master/docs/spfx/web-parts/guidance/tutorial-share-data-between-web-parts-global-variable.md

Is this what you are looking for?

https://github.com/SharePoint/sp-dev-docs/blob/master/docs/spfx/web-parts/guidance/tutorial-share-data-between-web-parts-global-variable.md

The article talks about setting up two different WebParts that use a single central data store to access data which means that you can share data between the two distinct WebParts and you can deploy either of them individually without a requirement on the other as Heinrich stated. It should allow communication between the two WebParts as he wants