By Bill Dedman, Investigative Reporter, NBC News

A long-lost relative of the reclusive heiress Huguette Clark, who could have inherited $19 million of her $300 million fortune, has been found dead under a Union Pacific Railroad overpass in Wyoming.

Children sledding found the body of Timothy Henry Gray, 60, Thursday afternoon in Evanston, a small mining town in southwestern Wyoming near the Utah border. The coroner said it appeared he died of hypothermia. The low temperature that day was 10 degrees, and had hit zero in the previous week. Lt. Bill Jeffers of the Evanston Police Department said there was no evidence of foul play, and Gray was wearing a light jacket. Gray's siblings said they hadn't heard from him since their mother's funeral in 1990, when he disappeared without a word. It wasn't clear whether Gray was living under the overpass, where transients have been known to camp.

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Tim Gray was an adopted great-grandson of former U.S. Sen. William Andrews Clark, known as one of the copper kings of Montana, a banker, a builder of railroads and the founder of Las Vegas. The senator's youngest daughter, Huguette Clark, was a recluse who died in 2011 in New York City at age 104, after living in hospitals for 20 years while her palatial homes sat unused. Gray was her half great-nephew.

In her will, Huguette Clark left no money at all to her family, leaving it instead to her nurse, goddaughter, attorney, accountant, hospital, doctor, favorite museum and various employees, as well as to an art foundation to be set up at her oceanfront estate in Santa Barbara, Calif. None of her relatives had seen Clark in at least 40 years, though some had been in touch with her through holiday cards and occasional phone calls.

Nineteen of Clark's relatives have stepped forward to challenge her will in a New York court. A public administrator joined the challenge on behalf of Gray. When lawyers tried to find him to let him know about the Clark estate battle, they found his belongings had been abandoned in a storage locker, according to court records, and private investigators were not able to find him.

If the relatives win their court challenge, Gray's estate would be entitled to about $19 million before taxes, or 6.25 percent of Clark's copper mining fortune, which has been conservatively estimated at $307 million by the administrator of Huguette Clark's estate. If Gray, who apparently had no spouse or children, died without a will, his siblings would receive his share in addition to their own.

Gray was not using the money he already had. The coroner said Gray's wallet contained a cashier's check, from 2003, for "a significant amount."

Gray's older brother, Jerry, said Tim had worked as a cowboy and lived in the Rocky Mountain states. "He was homeless essentially. If we had proper mental health services in this country, we could have been notified and known to do something."

Huguette Clark attracted the attention of NBC News in 2009 because of her vacant but well-manicured mansions and questions about the management of her money. The battle over her estate could go before a jury in 2013, though settlement talks have begun.

The archive of Clark stories, photos and videos is at http://nbcnews.com/clark/.

Do you have information on the Clark family?Reporter Bill Dedman is co-authoring "Empty Mansions," a nonfiction book about Huguette Clark and her family. If you have documents or information, you can reach him at bill.dedman@msnbc.com.

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