Marvin Humes, Aston Merrygold, JB Gill and Oritsé Williams of the boyband are currently on their 'Goodbye' farewell tour, and were unaware that their other halves had planned the surprise!
Marvin, who is married to The Saturdays star Rochelle Humes, was overjoyed when she brought along their baby daughter Alaia-Mai to join in on the fun.
Alaia-Mai looked cute in her black tutu and bright green top with the words, 'Green Princess' emblazoned on the back.
Proud dad Marvin looked over the moon to have his family there to support him, and later shared a hug with his daughter. Captioning the snap, he said: "Daddy got surprised today by his Green Princess!"
Rochelle, who also wore a green top with the word 'Marvelle' emblazoned on the back, even joked that she had joined a new girl group called "JL-YES."
The 24-year-old said on Twitter: "Last night was so fun! Love it when a surprise come off." She later added: "Wife and mum = best job."
Meanwhile, AJ Azari shocked boyfriend Oritsé when she turned up to the venue. Taking to Twitter, Oritse said: "@AJAzari @RochelleTheSats @sarahsugar84 @ChloeTangney proper surprised us hahaha!!! Wow #ImBaffed."
AJ and Oritsé, who were crowned winners of ITV dance competition Stepping Out in September, made a short Instagram video, which showed AJ rocking her bright red T-shirt in support of her beau!
Coming to support Aston was his dancer girlfriend Sarah Richards, while Chloe Tangney surprised boyfriend JB.
After the surprise went down without a hitch, Chloe said: "We all surprised our boys in Brighton!! Well done girlies @rochellethesats @sarahlourichards @ajazari."
JLS' tour marks the end of their career as they plan to go their separate ways after six years together. Sob!
Even though they won't be performing together anymore, they will still remain the best of friends.
Speaking to Reveal earlier this month, Marvin said that their split came "at the right time".
"The great thing about the four of us is we are still friends," he told us. "We've not had arguments or fallouts and we still socialise together and that will continue. It's going to be like we haven't split up in a way because we will still socialise like we do now."
Watch JLS' music video for 'Billion Lights' below: