A Fort Worth man faces up to 21 years in prison after he admitted lying about his military service to get a mortgage-free house and monthly veterans' benefits.

Brandon Blackstone claimed to have received a Purple Heart when his Humvee drove over a bomb in Iraq and it exploded.

"I was blown up while I was there," he said in a 2012 interview with NBCDFW. "I had to be medevaced home."

He offered more details about the explosion in a YouTube video.

"The one (Humvee) behind me got totally destroyed," he said. "I suffered a head injury and a head laceration that caused traumatic brain injury."

Blackstone pleaded guilty in federal court in Dallas to making up the story and will be sentenced in February, The Dallas Morning News reported.

Blackstone's attorney, Justin Sparks, did not return a telephone call from NBCDFW.

But he told The DMN that his client served his country and still suffers from post-traumatic stress disorder.

It turns out Blackstone may have taken more than money.

The sister of another Marine who served in the same unit said Blackstone stole his story.

Lezleigh Kleibrink, of Trophy Club, said what Blackstone claimed happened to him really happened to her brother, Casey Owens.

Owens did receive a Purple Heart after the Humvee he was in blew up.

He somehow survived but lost both legs, broke almost every bone, and injured his brain, too.

"He was absolutely a hero," his sister said.

The truth is Blackstone never received a Purple Heart.

He came back to the U.S. after a month overseas – not with a war injury but with appendicitis.

And a story.

"It was Casey's story, minus his legs being gone," Kleibrink said.

Blackstone accepted a mortgage-free house, and monthly veterans' benefits he now admits he didn't deserve.

Owens tried to adjust to life back home. Even without legs, he skied in Colorado.

But his sister says he had trouble coping. He died in 2014.

"In a very manic moment, he took his life," she said.

Kleibrink said she is no longer angry but still wonders why Blackstone lied.

"It just brings all of this back up," she said. "Now I'm left sitting here looking at pictures. This is all I have left."