The former Leeds teacher could not conceal her joy, celebrating alongside Hollywood actor Russell Crowe, as Sam, Luke and twins Tom and George Burgess helped South Sydney to a 32-18 win over Wests Tigers to go top of the NRL.
They became the first set of four brothers to line up in the same Australian side for more than a century since Ray, Roy, Rex and Bernard Norman all turned out for the now-defunct Annandale club in 1910.
It was also the only the third time that four Englishmen have played first grade for the same team in Australia.
Lee Crooks, Des Drummond, Deryck Fox and John Henderson did it for Western Suburbs in 1986, while Ken Ford, Derek Hallas, Mike Jackson and Ivor Lingard played together for Parramatta in 1964.
The Dewsbury-born brothers, who have a combined weight of 460 kilos, were all on the pitch at the final whistle and were quickly joined by their jubilant mother, who moments earlier was seen jumping for joy after oldest son Luke had scored his first try for the club.
"I'm overwhelmed," Julie told television summariser Brad Fittler.
"I couldn't believe it when Luke scored that try, that was the best thing ever."
It was an especially sweet moment for Sam, 24, the former Bradford forward who was the first of the brothers to sign for the Rabbitohs after being courted by joint club owner Crowe four years ago.
"It's something we dreamt of as kids but we didn't expect it to happen this quickly," said Sam.
"It's fantastic and great credit to the twins for how they've come on in the last two years. I'm really proud of the family but, to be honest, we've got a great team.
"The team is our family and we've been working extremely hard."
Tom, who completed the set of Sydney-based brothers when he left Bradford at the end of last season, said: "It's a great feeling, being on the field at the end there.
"That last tackle together was great, one to remember for the family."
Sam was also a tryscorer, making up for his fourth-minute sin-binning when he was yellow-carded for a professional foul.
Wests Tigers, coached by former Bradford boss Mick Potter who gave Tom his debut in Super League, took advantage of the extra man to take an 18-0 lead with tries from Tim Simona, James Tedesco and Ben Murdoch-Masila, all converted by Benji Marshall on his 200th appearance for the club.
However, Souths clawed their way back to 18-12 by half-time and drew level when Sam Burgess powered his way over for a solo try early in the second half before finishing the stronger side to run out comfortable winners.