The 19-year-old from Heathcote brought up his maiden victory at Geelong on Wednesday night, aboard the 11-year-old pacing gelding Realy Under Fire.

It was not only a proud moment for Sean, but for his entire family, headed by his father and harness racing legend Jim O'Sullivan, who has trained the much-loved Realy Under Fire since February 2018.

Equally chuffed was Sean's sister, 22-year-old Shannon, who duly celebrated her brother's success with a driving victory of her own four races later behind Monsieur Delacour for Ross Creek trainer Stephen Clarke, to ensure everyone in the O'Sullivan household went home a winner.

A breakthrough win for Sean O'Sullivan arrived in his 20th race drive, but not before an untimely and frustrating setback only weeks into his career last year.

The third-generation driver gained his licence last October, only to have it revoked following a tricky and testing drive aboard Majadore and was quickly ordered back to the trials by stewards.

Naturally disappointed, he took the blow in his stride and vowed to work twice as diligently to get his fledgling career back on track.

"She was a bit of a hard horse to handle and she pulled on me and hung out, so the stewards took my licence off me," O'Sullivan said.

"I had to do 15 more trials. I was a bit devastated it happened and dad wasn't too happy, but we fought back and I've come out of it a winner."

Realy Under Fire was beautifully rated in front by O'Sullivan and was able to put away his rivals after shooting clear early in the straight, on the way to a 5.7m victory at odds of $20.30.

While O'Sullivan admitted to having no expectations of notching up a win this early in his career, a gut-feeling before Wednesday night's race had him thinking his luck was about to change.

"I kind of knew in the preliminary, he felt a bit keen and I said to myself that he might prove a few people wrong," he said.

"He was pretty high priced in the betting and no one really picked him to run anywhere because it was a 2100m race - that's usually not his go.

"I was pretty confident coming into the straight the last time and when I looked around and saw I was catching a few lengths off them, I was very excited.

"I gave the whip a bit of a wave and I let out a bit of a yell. It was a pretty good feeling."

Sean could not have been happier to have achieved his first win behind Realy Under Fire, a horse, who holds a special place in the hearts of the O'Sullivans.

The veteran pacer also provided Shannon with her first winning drive for her father, at Echuca in September 2018, though not her first race win.

"He's doing a pretty good job the old horse, hopefully there are a few more wins in him," said Sean about Realy Under Fire, who has won 16 of 205 career starts, six of them since his move to the O'Sullivans.

"To win it for dad was pretty special. It made for a nice trip home from Geelong, it was all winners in the car, including the horse."

Realy Under Fire's victory at Geelong was his first in 15 starts since a winning effort at Charlton last November.

There was no one prouder at Geelong on Wednesday night than Gordon Rothacker medallist and 1987 Interdominion winner Jim O'Sullivan, who quipped he was now 'third in line in the family' for prospective drives.

"Sean was beside himself, but Shannon being Shannon, she couldn't let him get away with all the bragging rights for the night, so she had to win one too," he said.

"They both did well, but especially Sean, he rated that horse really well.

"I thought he had a chance to win it, the horse has been going pretty good. When I looked at the field, I said to Sean we've been giving the lead away. He's a good leader, but he doesn't like being hammered.

"I thought if we could hold the lead, he's a pretty good front-runner, but he rated him well.

"It wasn't his pet distance, but he has won a few races over the trip. He generally likes the mile as he so fast out of the blocks.

"But over the longer distance, (his rivals) don't tend to come out humming as much, which doesn't suit him."

O'Sullivan, who has amassed more than 2000 winners as a trainer and driver in a career spanning more than five decades, credited Sean's foray into race-calling as integral to his development in the sulky.

The teenager has been calling the trials at Bendigo in recent months, giving him a new perspective on race-driving.

"There's no doubt the calling benefits his driving; it teaches him where the horses are and what to look out for," he said.

"He called nine trials at Maryborough on Sunday morning and he also does Bendigo.

"It does him the world of good. I'm sure the second win won't be too far away."

While Jim insisted neither Sean or Shannon emerged from Geelong with the clear bragging rights, that might not be the case this Sunday night at Cranbourne.

The siblings will go head-to-head in race eight on the card, with Sean aboard Danman for his father and Shannon taking the drive on the Ash Warton-trained Trent From Punchy.

Danman is chasing his first win since July 2019 at Cranbourne, when he was ironically driven by Shannon.

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