They figured he was just an especially proud big brother, perhaps with a penchant for exaggeration. After all, Nick Thompson's kid sister, Lexi, was just 6 when he went off to Georgia Tech.
"But she was already good by then; scary good," said Nick, 31, as if he were still making his case. "I would tell my college teammates and guys I knew, Watch out for her, she is going to be sooo good.
"Now it's the coolest thing because these guys are on the PGA Tour with me and they come up to me and they're like: 'Wow, you really called it. We thought you were just talking up your sibling, saying your little sister was the best. But she really is.'"
Less than two months past her 19th birthday, Lexi Thompson became the second-youngest player to win a major championship when, in typically aggressive and ultimately comfortable fashion, she cruised to the Kraft Nabisco title April 6 by three strokes over closest competitor Michelle Wie.
As usual, both older Thompson brothers -- Nick and Curtis, 21, a junior on the LSU golf team -- were mentioned in the afterglow, with father Scott brushing off credit by saying: "Everybody asks what I did. She had two older brothers to follow. It was easy for me."
But their father's modesty aside -- "My parents are the ones who deserve all the credit," Nick said -- it is also patently clear that Lexi's monstrous ball-striking ability and her killer instinct, honed on countless hours of trying to keep up with Nick and Curtis, also account for her steady rise to the top. It was obvious on that final Sunday that the Thompson family's competitiveness extends beyond the "Backyard Five," which the siblings dubbed the five holes that wrap around their home at TPC Eagle Trace in Coral Springs, Fla.
Even as Nick rushed to make a plane home, where he would watch Lexi's last holes on television after he tied for 24th at the Shell Houston Open, and Curtis played 36 holes in leading his team to a share of the Aggie Invitational, there was an internal competition going on.
"I was watching on my phone," Curtis said, "and after the 15th hole, I said, This is over; she is smart enough, I don't need to watch anymore. So I sent her a text telling her 'Great job. Congrats on the win,' just to be the first one."
A bit horrified at his younger brother's potentially jinx-inspiring confidence, Nick quickly tried to one-up him.
"I guarantee you, I was the first one after it was official," he said. "I had it all written, and as soon as she sunk that little14-inch putt, I hit send. I don't do anything like that until it's final and done."
A week after it was final and done, Nick was on the course back home with Lexi, one of the rare occasions the siblings have been able to spend together since Lexi turned pro at 15. It made him immediately reminisce about one of his favorite big-brother tactics when Lexi was younger.
"Of course, I have that protectiveness with her," he said, "but I was also out there to rattle her trap and get her going, fire her up. I guess that's my job. Maybe it was just saying something irritating, so when something came up during a tournament -- there's always some dummy in the crowd, noises, anything -- it wouldn't bother her so much. It would make her stronger."
Lexi said she does not remember anything terribly harsh. "More of a little trash-talking," she laughed. "I always remember both of them being pretty tough on me when we played each other. It made me more determined to beat them, and it's where I got my determination on the golf course."
But it was the younger Thompsons who were together most often. They're separated by two years, three months, and they were home-schooled online to accommodate golf. They were even mistaken for twins.
Two years ago, Curtis put on a blond wig and dressed as his favorite women's pro for Halloween.
"I sent him one of my outfits," Lexi said. "He's a little tanner than me, but it was close. It was pretty weird."
Curtis echoed: "You put long hair on me, and we're the same person. On Halloween, it was definitely weird. People figure out pretty quickly I'm her brother."
But it was still the competition that consumed and drove them.
"We butted heads until basically we had to separate because she turned pro and I went to college," Curtis said. "Now, we hang out and it doesn't matter, but it could be anything when we were growing up -- pingpong, who could fold their clothes faster -- it didn't matter.
"Without competition, we're just two normal people, but I can't even imagine our relationship without competition. It would just be weird."
Curtis said he was never threatened by the fact that the sibling often beating him was not just younger but a girl.
"It was definitely not a guy-girl thing," he said. 'I've seen a lot of girls play, and she's a completely different animal than any other golfer I've ever seen. She has a special thing going for her."
He said it goes further than her ability to drive the ball. It's her drive, period.
"Even if she has a good time one night, going bowling or hanging out at a restaurant, she'll still be out there first thing every morning working harder than ever," he said. "She has more persistence than most other people."
It has served as a lesson to Curtis, whom Nick calls the most talented of the three.
"Lexi has worked to where she's at," said Curtis, ranked 29th in Golfweek/amateurgolf.com. "And I'm not really sure where she got her determination because she was always a notch above everyone else in junior golf. I was also a notch above between about 10 to 15 years old, then I was like, All right, I can slack off. And that's when everyone caught up to me, until I realized I had to work at it as well."
Lexi said she agrees with Nick that Curtis is the most gifted of the three. She recalled coming up with contests on the course to keep the younger Thompson brother motivated.
"He'll pull off shots on the golf course where I'm just like, Wow, I can't believe he just did that," she said. "I know I can learn so much from him. ... I know I can go to both of them because they know my game so well. I went to the range with Curtis the other day, and he helped me right off the bat. It's always nice to have them around."
Nick remembers his little brother and sister on the course at 4 and 5 years old.
"Between the two of them, they were amazing," he said. "You could just tell they had something, the way they swung the club, the way they hit it. I really saw it."
The almost paternal pride is still there, even as he talks about watching one of his, and the Golf Channel's, favorite clips.
"It's always on," he said. "Lexi was 8 or 9, just a little tyke. And she taps in a putt to win a tournament and walks over to my dad and huddles right next to him. Every time I see it, I laugh. It's my little sister and she was so young and adorable. I just giggle."
What he does not enjoy seeing on the Golf Channel or anywhere else, is his kid sister's game being criticized -- specifically her putting, a frequent source of discussion.
"I love when they say that on TV," he said sarcastically, "if not for her putting, she would be better. But her putting is never going to look as good as the majority of people because she hits the ball so well, she generally hits more greens than other players. When you do that, your average distance from the hole on your first putt is further. But she is a very good putter. And she can get really streaky good."
At 12, Lexi was the youngest player ever to qualify for the U.S Women's Open. At 15, the same year she turned pro, she finished as runner-up at the 2010 Evian Masters. She joked recently that she feels a lot older than she is. Nick does not disagree.
"She's getting older, and every round out there she's learning more about herself and the game," he said. "She's only 19, so she has not had that long to learn, but she is learning now and that's why you're seeing her win twice at the end of last year and her first major now, which is her fourth professional win. The sky is the limit for her. She is that good."
Nick, once Golfweek's top-ranked amateur in the world and a four-time NCAA All-American at Georgia Tech, finished sixth on the Nationwide Tour money list in 2007. He was 20th in the FedEx Cup rankings in '08 with six top-10 finishes.
The parent of a 6-month-old son, Nicholas James, with wife Christen, he likes to joke that he is now known as "Lexi Thompson's brother."
But how astonishing was it when his baby sister won her first major?
"It was a cool moment, an amazing moment," he said, "but did I have to pinch myself? No, because once I saw and heard how she was hitting it, and her scores were showing me, I was like, She's ready, she going to win. She's really good."