Twins Josh and Kyle Brooks, 17, were suspended from the first X Factor live show on Saturday night following allegations about Josh's personal life. They later agreed with producers they would leave the competition.
Four of Diamonds has now been drafted in as a replacement.
Hearing the news, the Brooks twins tweeted: "So, so happy for you girls! You deserve it!"
The band replied: "Thank you so much boys."
Josh and Kyle also shared a new selfie with fans overnight, showing them flashing matching big smiles at the camera. The image was liked more than 2,000 times with dozens of fans saying they were sorry to see them go.
The twins' departure came after allegations that Josh had been violent towards an ex-girlfriend and sent her threatening messages.
In a statement on Monday, Josh said: "By mutual consent, we feel like it was best to walk away from the show this year. While not everything that has been claimed is true, I would like to apologise to everyone involved. And would like to thank everyone for there ongoing support and love."
The statement continued: "A huge thank you to the team at @TheXFactor and @ITV for all your hard work and all you have done the last two years for us. And the final 10, we have loved every second of this journey with you all. We love you all dearly and wish you the best of luck. Miss you all."
Brooks Way entered X Factor last year as well but didn't make it to live shows. This year they did, being put through by groups mentor Louis Walsh.
Now Four of Diamonds have taken their place and will perform in this weekend's second live show which has a Motown theme. They said yesterday: "We are so excited to be back on The X Factor - we're really looking forward to performing live, working hard and showing everyone what we're made of."
Louis said: "I was really impressed with the girls at judges' houses but only had three spots to fill for the live shows. At the time a lot of viewers were disappointed that I didn't put the girls through, now that a place has opened up in my category, I've listened to the fans and am delighted to be bringing the girls back.
"They're a great girl group and I'm hoping will take me all the way to the final."