The post was soon flooded with well wishes from the couple's industry pals.
Home & Away's Sophie Dillman was visible in the comments, penning an enthused: "Happy 40th!!!!!"
MAFS alum Jules Robinson also shared a sweet: "Happy bday x."
Meanwhile, fellow presenter Larry Emdur took a cheekier approach, writing: "Happy birthday superstar @guysebastian , I hope @julessebastian gave you that Harley I dropped over XX."
As did Cameron Daddo, who made a playful swipe at Guy's Polo shirt.
"And he’s spent it on the golf course!" Cameron wrote. "Or is that the outfit you bought him and he’s given you a fashion show?? .. my bet is both! Well done and HBD @guysebastian."
During Jules' birthday celebrations last year, Guy penned his own tribute to the love of his life, accompanied by a series of family photos.
"Happy birthday @julessebastian You are incredibly kind and SO selfless in the way you love. Thanks for being authentically YOU in every moment. We know that with you we will get through whatever craziness life throws at us:-) ❤️Your boys," the musician penned.
The besotted couple originally met during childhood. Over time, they fell head over heels for one another and eventually tied the knot in 2008, welcoming two sons, Hudson and Archie, along the way.
As they grow together, they admit they continue to discover new traits in one another that they find attractive.
“I probably noticed his character and that he was a good person at the start but I probably didn’t know it in as much detail as I know now watching how Guy lives his life, how he interacts with people, his integrity, his patience, his professionalism,” Jules told WHO in March.
“All those things, I sort of subconsciously knew that was inside of him but it was never really brought to the surface until life really kicked off and all those things were put to the test and he really has just remained a good person at the end of it all. Not that we’re at the end of it all!”
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