In Odoo 12 and earlier, this is possible by defining parent and child companies.  Odoo will (generally) allow users in the parent company to view data in the “child” companies, but not allow users in one “child” company to view data in another “child” (or “sister”) company.

In Odoo 13 there are checks that the contact is either in the current company or the company is blank, so this would need some customization. 

More information here: https://odootricks.tips/multicompany-in-odoo-13/

Same issue with sharing product multi company as well as sharing product with multi website. Is there any reason why odoo 13 come with this default setting ? I have founded a module to solve multi-website sharing product. But there are no module to solve the problem with Multi-company-product ad Multi-company-Contact.