BEHIND her sunny smile and blazing hot career, country music queen Faith Hill hides a heart­breaking family secret – her brother is a convicted felon and former crack addict!

The ENQUIRER has tracked down Faith’s long-lost sibling, and in a blockbuster exclusive interview, he bares his soul to reveal how the “Breathe” singer and her superstar hubby Tim McGraw saved his life.

Now a source says Faith’s grateful brother, Zachary White, has returned the favor by helping the high-profile couple cope with their stormy marriage and possibly dodge a devastating $135 million divorce.

“I made my share of mistakes in the past, but Faith showed me that I could be a better person,” 43-year-old White told The ENQUIRER.

“I turned my life around, and I owe much of that to Faith and Tim. If it weren’t for them, there’s no telling where I’d be now.

They’re both amazing, down to earth people. Their love and support have been nothing short of extraordinary.”

White’s legal troubles began in November 1990 when, according to a police report obtained by The ENQUIRER, he was arrested in Winter Park, Fla., after trying to snatch a woman’s purse outside a Bakers Square restaurant.

White fled the scene, but he was soon caught, identified by the victim and charged with strong-arm robbery. He reportedly confessed to police that he tried “to take the victim’s purse to support his crack cocaine habit.”

The admitted drug addict also told cops that he’d grabbed another woman’s purse four days earlier in the same parking lot.

Nearly two months later, Winter Park cops busted

White again after he stole a silver-colored Mazda, and extorted the vehicle’s owner by demanding $200 for its return.

White pleaded no contest to a third-degree felony of grand theft and three misdemeanors. He was slapped with two 18-month sentences of community control and ordered to complete a one-year residential program that included drug counseling.

Meanwhile, Faith – who’d been put up for adoption at birth – began looking for her biological family. In 1993, she found her mother, Paula White, and her brother. She also learned her father, Edwin White, died in a car crash when she was 10.

“Finding her family was one of the greatest blessings in Faith’s life,” said a source. “But it was heartbreaking to learn her brother had been struggling with a life of crime and drugs.

“For a long time Faith was embarrassed by Zachary’s criminal past and tried to hide it from her fans. But now that he’s straightened out his life, she tries to keep it secret to protect him.”

White says being reunited with his famous sister was the high point of his life.

“Faith is a beautiful, amazing person, and she’s forgiven me for the mistakes I made when I was younger,” White, a construction company owner in Port St. Lucie, Fla., told The ENQUIRER.

“We’ve become very close, and she welcomes me into her family every chance she gets. She and Tim have invited me into their homes in Tennessee, California and the Bahamas. Faith always lets me know she’s there for me.”

To thank Faith, sources say White has devoted himself to helping her and Tim work out the problems in their turbulent 17-year-old marriage.

As The ENQUIRER has reported, the couple’s marital troubles center around Tim feeling imprisoned by Faith, who he believes is controlling and demanding, and her outrage and jealousy over his wandering eye.

“Zachary has actually been great for their marriage,” said the source. “He’s acted as a mediator between Faith and Tim during some of their worst blowups and helped them talk through their problems. In some ways, Zachary has saved Faith and Tim’s marriage – at least for now.

“In the end, their marital woes may be too great to overcome. But it’s remarkable that after Faith and Tim helped her brother straighten out his life, Zachary is returning the favor by trying to keep them together.”