The family of a Wharton firefighter who died battling a massive egg farm blaze is fighting to keep his widow from receiving death benefits, arguing that the 37-year-old had found out his bride of two years was born a man.

Thomas Araguz III separated from his wife after learning her history two months prior to being trapped in the fatal July 3 fire, according to attorney Chad Ellis, who is representing Araguz's parents in the lawsuit.

"He was distraught. It was extremely difficult and embarrassing for Tommy," said Ellis, who added that there is no will for the estate, which will be substantial since the fire captain died in the line of duty.

Thomas Araguz learned during a custody dispute with his ex-wife last spring that 35-year-old Nikki Araguz, whom he married in August 2008, was allegedly born as Justin Graham Purdue. Ellis said he was unsure when Nikki Araguz may have undergone a sex-change operation, but the lawsuit claims she changed her name in the mid-1990s to Nikki Paige Araguz.

Nikki Araguz has been court-ordered not to remove any property from their home, withdraw funds from any account or receive any death benefits, as part of the lawsuit filed last week in state district court by the firefighter's mother, Simona Longoria.

Among the issues: Who will be the administrator of the estate and whether Nikki Araguz was Thomas Araguz' lawful wife. The family wants all the death benefits to go to the two young sons that Araguz had with ex-wife Heather Delgado.

The lawsuit, slated for Friday in Wharton County District Court, leans on 1999 state case law prohibiting same-sex marriage and maintaining a person's gender forever remains the same as it was at birth, Ellis said.

"We are not blazing new legal ground here," Ellis said.

Nikki Araguz declined Sunday to discuss her gender history, and insisted that her husband knew everything about her personal life when they married in August 2008. She also said the couple was not separated.

"We had a completely honest marriage, a 100 percent loving, honest marriage," she said. "I am grieving the loss of my husband and best friend."

She also would not discuss her birth name or whether she was connected to the criminal history of Justin Graham Purdue, which includes at least three theft convictions.

Nikki Araguz, a native of northwest Houston, ran an unsuccessful bid for Wharton mayor against a volunteer firefighter this past spring, drawing 30 percent of the vote. She closed her magazine, Wharton County Living, immediately following her husband's death.

Another issue at play: Only a spouse may file a wrongful death suit, Ellis said.

The Bureau of Alcohol, Tobacco, Firearms and Explosives and the state fire marshal have said the fire — which required 150 firefighters from 31 departments — was caused by a light fixture.

paige.hewitt@chron.com