Are we able to do this all ourselves since nothing is being contested?

Just an FYI, none of the parties had wills. While my parents were alive, they quitclaim deed their house to my sister but had a life estate clause to live there. Fast forward, my mom passed away and then my sister passed away. After that, my dad then filed a warranty deed for the same property to my brother. He assumed the property was still his and didn't realize he didn't own it. Now my dad is passed and we found out that the property belongs to my brother in law (deceased sisters husband). We know this because an attorney told us via a title search. Is the warranty deed worthless? It was filed and recorded. We are trying to get the house and all parties are willing to sign anything they need to. So can my brother in law just quitclaim deed it to us? And then, can we file a quiet title claim against my brother which he will not contest?? Also, the attorney we tried to hire seems to have no interest in our case and we are trying to do this on our own.