If two buyers are assigned to the same company in your contacts, they will see each other's orders.
When two buyers are assigned to the same Company in your Contacts, you will be able to select the company name and under 'Buyers' see both buyers names and emails:
Or, if you are utilizing the old Contacts page view, on the righthand Contact Card that appears after selecting a Company, expand the 'Buyers' menu:
The buyer selected on the order will receive the order confirmation email, but all buyers for the company will have access to view these orders.