The colt appeared suddenly on her television screen, surging from 16 lengths behind on a sloppy track he loved. As Exaggerator splashed to a 6¼-length Santa Anita Derby triumph, a 72-year-old grandmother acted like she had hit a life-changing Pick 6.

The living room celebration on Placide Road in tiny Maurice, Louisiana, had nothing to do with money, although Brenda Desormeaux could not have been more heavily invested. The winning trainer was her firstborn, Keith. The rider was Kent, his brother. “I’ve seen hundreds of Kent’s races, and I was screaming and hollering like I’d never seen one before,’’ she told Newsday.

On Saturday, Keith, 49, and Kent, 46, will try to become the first trainer-jockey brother combination to win the world’s most coveted race, the Kentucky Derby.

“It’s something you fantasize about but never think will become reality,’’ Brenda said. “It’s almost a miracle, a dream come true for the parents and the boys. There’s been a lot of excitement in our little metropolis of Maurice. NBC was here six hours doing a feature.’’

The other siblings who tried to win the Derby together didn’t come close, with Nick and Jimmy Combest seventh in 1964 and the Romeros, Gerald and Randy, 12th in 1993. Hall of Famer Kent Desormeaux has won the Derby on Real Quiet (1998), Fusaichi Pegasus (2000) and Big Brown (2008). For Keith, it’s his debut.

“This is a Hollywood story for me,’’ he said. “It’s old hat for Kent. For me, it’s surreal . . . It’s still sinking in that we’re here.’’

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Misfortune kept the Cajun brothers — the Meaux Breaux, as Kent tweeted — from collaborating in last year’s Derby. Texas Red’s easy win in the Breeders’ Cup Juvenile made him the winter-book favorite, but a foot abscess knocked him out of the Triple Crown.

Keith and Kent are bright, articulate and funny but have opposite personalities. Keith is measured and reserved, like their father, Harris, and Kent’s a crackling live wire liable to say anything. The source of Kent’s gift of gab is obvious. “Oh yes, he got that from his mother,’’ Brenda said, laughing. “Harris says I talk enough for the both of us. Keith is more like his father, a lot more serious than Kent.’’

The brothers’ career arcs also are nothing alike. No jockey ever achieved so much so quickly. Starting in 1987, at 17, Kent led the nation in wins for three consecutive years, including a record 598 in 1988. “Kent was an overnight success,’’ Brenda said, “but not Keith.’’ While his kid brother became rich and famous, Keith was vocationally vague.

“Kent knew what he wanted to do when he was 12,’’ Keith said. “As a kid, big-time racing on TV was a fantasy to me. Having a career in it never grabbed hold of me until my second year of college, when Kent started to be so successful.’’

While Kent excelled at the elite level, Keith paid his dues in Maryland, Louisiana and Texas. Brenda has called him “kind of a nomad,’’ and he won only 39 races from 1988-95. He began getting high-class horses four years ago and won three seven-figure stakes in the past 18 months.

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But Kent has had his struggles. He acknowledged a problem with alcohol in a 2012 interview with The New York Times. “You have to accept that the alcohol has gotten control of you,’’ he said, “and once you understand that, you can start moving toward other steps.’’

In July 2010 Kent failed a Breathalyzer test at Woodbine, according to track stewards. On May 18, 2012, he failed another at Belmont Park, and on June 26, 2014, it happened again at Santa Anita, according to track stewards. Santa Anita’s stewards fined him $2,500 last Oct. 5 for riding “under the influence of alcohol” on July 29, 2015, at Del Mar.

“Kent has a drinking problem, as everybody knows,’’ Brenda said. “Keith tries to get him to stop, and they get into it about that. They’ve always been close personally but there was a rift professionally, and it was all about the drinking. They have a mutual admiration society, but they are brothers.’’

Kent’s been married for three years to apprentice jockey Rosie Higgins since divorcing Sonia, the mother of his sons, Joshua, 23, and Jacob, 17, in 2012. He’s on a riding roll this year (20-percent winners) and pumped. He flew Friday from California to Louisville, slept on Keith’s couch and worked out Exaggerator 5 furlongs in 1:02 3/5 on Saturday. Then he caught a return flight so he could “mount steeds” at Los Alamitos.

Keith and Kent rented three houses for their Derby entourage of 20, including their sisters, Kristie, Kelli and Kalen, brother Kip and Keith’s son, Bailey, 24. Brenda and Harris attended Kent’s three Derby wins and are praying for number four. “It would be out of this world,’’ she said.

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Keith isn’t predicting Exaggerator, 4-for-9 lifetime, can beat 7-for-7 favorite Nyquist. “We’ve tried him three times,’’ he said. “All I can hope is that my horse is maturing and becoming faster and that Nyquist is leveling off.’’

Nothing could thrill Kent more than to lift the solid gold trophy with his big brother. “It’s extra special to be with Keith,” he said. “We don’t talk about it much. It’s all quite understood.’’