Adult sisters in Chicago were told by a local hospital that they needed to decide whether or not to remove their brother from life support, a lawsuit claims. They consented, and the man died.

But days before the funeral, their brother, Alfonso Bennett, turned up alive, returning home from an out-of-town trip, the suit says.

It turned out that authorities had misidentified the man who had been on life support with severely disfiguring injuries to his face. His real identity was Elisha Brittman.

Now, the families of both men are suing the city and the hospital, claiming they failed to properly identify Brittman prior to his death and ignored Bennett's sisters when they raised concerns.

Rosie Brooks of Chicago received a call from Mercy Hospital and Medical Center on May 13 telling her that her brother, Bennett, had been hospitalized for severe facial injuries and was on life support, according to a lawsuit filed Wednesday in the Circuit Court of Cook County, Illinois.

In April, weeks before Brooks was contacted, Chicago police found a naked, unconscious man underneath a car with facial injuries so severe it left him "distorted," the lawsuit states.

The man did not have identification on him and was taken to the hospital as a John Doe. He remained listed as a John Doe until Chicago police “incorrectly identified” him through a mugshot as Bennett, according to the lawsuit.

According to the suit, Brooks and her sisters told doctors multiple times that they did not think the man in the hospital was their brother.

“Rosie Brooks and her sisters were repeatedly told that he was and that they needed to accept it,” the lawsuit states, adding that hospital staff told them they were in denial “because the situation was a difficult one to handle.”

On May 20, the family was told they needed to remove the man from life support and they did. The man died on May 23.

As the family was finalizing funeral arrangements, Bennett returned home. The family immediately contacted the funeral home and the body was fingerprinted and correctly identified as Brittman.

"Elisha Brittman died, at least in part, because Mercy Hospital convinced people, not authorized to make medical decisions on his behalf, to make life affecting determinations that were a proximate cause of his death," the suit states.

A Chicago police spokesman told NBC News on Friday that an internal affairs investigation was opened to determine if proper protocol was followed when identifying the man. A death investigation was also opened to determine how Brittman died.

Mercy Hospital said it is "not providing a statement at this time."

The lawsuit states that the ordeal was "extremely taxing" on both families. Brooks, at least three of her sisters and Brittman's niece are all seeking at least $50,000 each.

The city of Chicago told NBC News on Friday that it has not received the lawsuit and cannot comment.