Bill Bowlen's reasoning is "due to their failure to uphold Pat Bowlen's wishes and act in the best interest of Pat Bowlen, his family and the Broncos," according to the filing.
Joe Ellis, Rich Slivka and Mary Kelly have served as trustees since Pat Bowlen stepped aside in 2014 because of Alzheimer's.
"I am a huge fan of the Broncos, and have been for decades. Unfortunately, over the past 15 years, I've noticed that the operation of the Broncos has deteriorated, while my brother's health has worsened," Bill Bowlen said in a statement. "I have real concerns with these trustees, their conduct and how they got to the positions they are in. They have little or no accountability to anybody but themselves. They have not complied with the rules of the NFL and I am uncomfortable with the way they have handled my brother's affairs. I know what his wishes were, and these individuals are definitely not following them."
Bill Bowlen is asking the courts to name an independent party to serve as conservator of Pat Bowlen's estate.
In a press release, Bill Bowlen said: "The three trustees have refused to implement a long-term succession plan that adheres to Pat Bowlen's long-stated goal of ensuring that his children ... retain management and control of the team. Instead, the current trustees have done everything they can to delay Pat Bowlen's children from assuming management and control of the team, in violation of their fiduciary duties."
Two of Pat Bowlen's daughters -- Beth Bowlen-Wallace and Brittany Bowlen -- have expressed interest in succeeding their father, according to the Denver Post.
"We have not seen this lawsuit and first learned of it through a media report [Thursday night]," Dan Reilly, legal counsel for the Pat Bowlen Trust, said in a statement released Thursday. "Although we are currently reviewing this matter, we are aware that the counsel submitting this complaint on behalf of Bill Bowlen is the same one that has been representing Beth Bowlen-Wallace.
"The trustees will continue to execute Pat Bowlen's long-standing succession plan for the Denver Broncos in compliance with all NFL ownership policies."