Sounds like this has been creeping up for a while, with you and your brother not lifting a finger about it. Not like the mess with the septic is something you found out yesterday, right? And being the landlords, you take the rent money, but fail to maintain the property in a liveable condition. Now that the county is breathing down your neck, you want things quick and dirty.
Talk to a lawyer, especially if your brother is under a threat of violating some court order. Start the court process to legally evict the tenants, and ask the court for an extension, until this is completed. Check your own state laws about this. In reality, as a landlord, you should’ve had them memorised already. Do not do anything retarded, like lock them out or make their lives impossible, because this will be the tenant’s defense, and your eviction will get tossed.