Is There Any Way To Get Home Insurance To Pay A Claim In The Event Of Arson? 
You need to speak with an attorney in your area . I have seen similar situation where the innocent party is able to recover from the loss . It is similar to the fact that if there was a mortgage on the property and they were an additional named insured , they would have recourse even if the cause of loss was arson from the homeowner . This is a complex issue and I would expect that it is a large loss , therefore I do highly recommend you speak with a qualified attorney that practices in this field . 