Then I would go on every social media out there, such as Facebook, and totally destroy his reputation with facts.

We have two pets of our own, and we understand they are family members, but given all our real estate is purchased as an investment we do like the idea of pets destroying property (we know it happens!). 

How destroyed is the roof?

Looks like they are just trying squeeze money out and destroy your parents property.

Warning many relationships have been destroyed or seriously strained by business partnerships so I would exhaust other alternative, bank or seller financing ect. firstGood luck

But- I am willing to help as long as you don't destroy historic home haha 

Some were trouble-makers and were destroying my property.

Lightning hit the roof and basically destroyed it.

Destroy the acts, show the conduct and the contract falls as well as agreements to keep any money.  

If it destroys your life financially if the worst was too happen, the deal is too big and you need to scale back.Once your comfortable with doing deals, those items won't even be a concern anymore.