My company has 3 different products, 2 of them are more similar in the interface (one is an advertising/publishing platform, the other is a platform to publish web and mobile applications), and the third one (which is a social network) completely different, from the branding to the UI.
The problem that we are facing now is that there is not a strong consistency between all the products which is normal and fine, but when we produce corporate design (i.e. communication, presentations, pages on the corporate site) we struggle to find the common line between them and let them look like they are part of the same company. Another issue is that when we start a new project we always start without any benchmarks.
To solve this problem I've started to write design principles and style guides for each product, but my question is: does it make sense to write principles, and maybe some sort of general design style guide which can be applied to all of them, and the future ones? what are the cases in which such a scenario might actually make sense and why? Has anyone of you experienced something like that before and how have you handled it?
Thank you very much.