My dad just passed away and I am the only child in family. He did not have a will and has been living with a companion for over 20 years.

Dear Anonymous, I am so sorry for your loss.  As your dad's only child, you are entitled to EVERYTHING he had....EVERYTHING because be left no will...and I'm assuming there is no wife (you do not indicate if dad was divorced, separated or widowed). That means you have first dibs on being the Administrator (when there's no will, the executor is called an administrator). The big problem herein is that the companion has control of ALL of your dads assets and things quite possibly sentimental to you can begin disappearing.....so that means you need to quicken your pace towards putting things in place to become the Administrator.  The reverse mortgage, unless you desire to keep the house and you pay off what's owed, indicates the house should be sold....and the mortgage company won't deal with anyone but the individual designated by the court as the Administrator.  You do not indicate your dad owning additional assets, but if he does remember you want to keep things amicable with the companion so this won't turn into a wrestling match.  Try to include her as much as possible, but make it uncertain that you are in charge....she was obviously very important in your dad's live as you note over 20 years of involvement so your graciousness to her will get you a lot farther along than shutting her out.  Hope this helps and I wish you the best.