Kylie Minogue has reportedly being questioning why she wasn't "The One" following news of her ex-partner's engagement.

Kylie dated Olivier Martinez for four years, before splitting in 2007. The French actor and Halle Berry have been in a relationship for a year, and recently became engaged.

Kylie has since tweeted her congratulations.

However, despite being in a happy relationship with Andres Velencoso, the songstress is said to be reflective about Halle and Olivier's news.

"Kylie doesn't have feelings for Oli anymore, but she's wondering why she hasn't been The One," a source told British magazine Closer.

"Kylie wanted commitment and thought he'd propose, but he ended it, so it's playing on her insecurities how come he's now so sure Halle's The One after a year?"

Kylie and Andres have been dating since 2008 and are enjoying their time together; however work commitments are reportedly keeping them apart.

The 43-year-old star is said to have rubbished any plans that the Spanish model will propose anytime soon.

"She and Andres spent time together over Christmas, but she doesn't think a proposal is forthcoming as they work apart a lot," the insider added.

"She laughs off suggestions she's upset over Olivier, but something is bothering her. She's throwing herself into work."