GREAT Balls of Fire! Legendary rocker JERRY LEE LEWIS is getting mar­ried for the SEVENTH time – and once again he’s keeping it in the family.

The 76-year-old piano-pounding singer is tying the knot with Judith Brown – the ex-wife of his outraged cousin Rusty, The ENQUIRER has learned.

Incredibly, Rusty was married to Judith for 24 years before he claims Jerry Lee busted up their relation­ship.

The trouble-prone entertainer – nick­named “The Killer” – made headlines in 1957 when shocked fans learned he’d married his 13-year-old cousin – his third wife – Myra Gale Brown, Rusty’s older sister.

The child bride scandal got Jerry blacklisted from ra­dio, and the fiery performer almost vanished from the music scene.

While best known for such hits as “Whole Lotta Shakin’ Going On” and “High School Confidential,” Jerry had been far more than an entertainer to Rusty.

“All my life Jerry was like a second dad to me,” Rusty told The ENQUIRER in an exclusive interview.

 “I grew up with him since I was 3 and ended up playing drums in his band. What’s worse is that I’m his cousin and ex-brother-in-law. Of course, I’m disappointed in him – he shouldn’t have let any of this happen.”

Rusty, whose di­vorce from Judith became final in September 2011, says he caught Jerry and his wife red-handed.

“In 2010, I walked in on them and caught her rub­bing his legs – the way you’re not sup­posed to. I confronted her and said, ‘What the hell are you doing?’ and she denied anything was going on.

“She told me Jerry was like a father to her, too. She said, ‘I’m just trying to help Jerry out, he said his leg was bothering him.’ Of course, I didn’t buy it. Soon after, she began traveling with him, and they went to New York and Europe – I knew something was going on.

“One day out of the blue, she calls me and asks for a divorce. She’s been with him ever since.

“My ex-wife Judith has a proven track record of being a gold digger,” fumed Rusty.

“She’s always been after money – and took all of mine and spent it at the casinos.

“The crazy thing is that Jerry never liked Judith, and she used to say Jerry was dirty and that he stunk. But once she got the smell of his money, things changed.”

Judith is officially Jerry’s caregiver, but Rusty charges she’s pushing the rest of the family aside so she can take him to the cleaners.

“Once she marries him, I believe she’ll take all his money and hit the road.

“Jerry doesn’t love Judith – all he wants is a caregiver. As long as he gets his egg sandwich with hot sauce and gets to watch ‘Gunsmoke’ reruns, he’s happy.”