What can we do if the executor never settled estate?

My brother was appointed as executor of my father’s estate in 1993. Recently, I learned that assets are still in my dad’s name and the estate was never settled. I have asked for a complete accounting from my brother and he never complied. I just learned that he transferred my father’s house to my mother’s (ex wife from before he died) in 2002. I suspect he never filed tax returns as well as satisfying a loan of $110,000 made to him and his business partner a year before my father’s death. I have a copy of the note for the loan which my brother states is still active. The will stated all of my father’s assets should be split equally between the 3 siblings. Please advise.