Identical twins Josh and Kyle make up the duo, who first appeared on The X Factor two years ago.
Earlier this series, The Brooks were seen singing for the judges at the room auditions and reuniting with former mentor Louis Walsh, as their nan waited on outside.
"We auditioned for the show when we were 15 back in 2014 and got to Louis Walsh's judges' houses in Bermuda," the guys explained at their first audition. "When we didn't get through we were gutted.
"We can totally understand where Louis was coming from [when he said we needed more time] and there's a huge improvement from those two 15-year-old boys, we're glad to be back... fingers crossed."
Returning with "unfinished business", The Brooks won four yeses from the judges to sail through to bootcamp and onto six chairs.
On tonight's show, Louis said: "I sent them home and said come back when they're ready, let's see if they're ready tonight."
The Brooks performed Cher Lloyd's Want You Back and Simon Cowell wasn't sure, saying: "You were like two wind up toys.
"I'm not sure if you've got that commitment or professionalism to make it through to the live shows."
However it was up to Louis if The Brooks got a seat, and kept it...
The X Factor 2016's Six Chair Challenge airs tonight at 7PM on ITV with Xtra Factor live straight after on ITV2.