Sibling duo Same Difference are out of the X Factor, meaning Rhydian Roberts or Leon Jackson will take the title.
The brother and sister act hail from Portsmouth
Sean and Sarah Smith came third in the ITV1 show's public vote, robbing them of the prize of a £1m record contract.
"They are genuinely nice people and I am really gutted for them," said mentor Simon Cowell. Welshman Rhydian is now the bookmakers' favourite to win.
The remaining contestants will learn the results of the vote on ITV1 shortly before 2230 GMT.
Same Difference were first on stage for the live final, performing Mariah Carey's All I Want For Christmas Is You surrounded by dancers dressed as Santa's elves.
The show also saw Kylie Minogue, Jason Donovan and opera star Katherine Jenkins duetting with the contestants.
Leon - whose mentor is Dannii Minogue - cavorted with Kylie in front of a red grand piano during a jazzed-up version of her 1990 single Better The Devil You Know.
FINAL SHOW SONG CHOICES
Christmas song: O Holy Night
Duet: You Raise Me Up (with Katherine Jenkins)
Favourite song: Somewhere
Christmas song: White Christmas
Duet: Better The Devil You Know (with Kylie)
Favourite song: You Don't Know Me
Christmas song: All I Want For Christmas Is You
Duet: Any Dream Will Do (with Jason Donovan)
Favourite song: Breaking Free
In addition to the duets, each contestant sang a Christmas song and their favourite number from the competition so far.
Same Difference became popular with viewers thanks to their cheerful performances and cheesy costumes.
Mentor Simon Cowell championed the act despite initially calling them "potentially the most annoying people I've ever met".
Fellow judge Louis Walsh has insisted they should not have progressed so far in the competition and do not have a future in the music business.
Rhydian's performances have been a mixture of high camp and strong vocals, while Leon carved himself a niche as a swing singer.
The winner will release a single on Monday, which is likely to top the Christmas charts next week, following in the footsteps of the last two X-Factor winners, Shayne Ward and Leona Lewis.