Sales Rep role permissions and visibility

Our sales rep teams are state based. Each Sales Reps each have customers assigned to them. The current set up of their role access has the ' Employee Restrictions - Own and subordinates only' ticked. On each Employee card, sales reps have a supervisor assigned to them, which means that supervisor can see their own customers plus their subordinates.

How can I set it up so that the supervisor and their subordinates can see each other's customers?

To give context, there are multiple supervisors who each have subordinates. These supervisors are the manager of their sales rep state, and each subordinate that they are a supervisor of are also state based. All of their customers have a custom field on their customer card that is the state they belong to.