The Mirror reports that the make-up artist is worried he could have been having a relationship with Lauren while they were still engaged, and has confronted him to demand answers.
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Simon Cowell and Mezhgan Hussainy
A source told the paper: “The situation is absolute chaos. Mezhgan is furious with him and has been calling him to ask him questions but he wouldn’t answer his phone so she drove to his house."
Simon and Mezhgan announced their engagement in 2010, before splitting in 2011.
One of Simon's other exes, Sinitta is also said to have reacted badly to the news.
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Simon and Sinitta
The Daily Mail reports that the 80s pop star 'burst into tears' upon hearing the news, and allegedly said, 'it should have been me'.
She also posted a cryptic tweet just before the baby news emerged, writing: "Something has just happened ..half miracle, half nightmare! #WakeMeUpIWantToGetOff!!"
1. Nobody seems to know whether she's called Lauren or Laura. Or both. So let's get this one cleared up once and for all. It's definitely LAUREN. We think. (credit:Getty Images)
Lauren Silverman: 9 Facts In 90 Seconds(02 of09)
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2. She's 36. That's 17 years younger than Simon Cowell so yes, he is indeed *adopts nana voice* old enough to be her father, tsk tsk etc, etc. (credit:WENN)
Lauren Silverman: 9 Facts In 90 Seconds(03 of09)
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3. She is still technically married to one of Simon's bezzies, property developer Andrew Silverman. But according to Us magazine, the estranged couple have been 'unhappy for some time and a divorce is in the works'. Phew. (credit:Splash)
Lauren Silverman: 9 Facts In 90 Seconds(04 of09)
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4. She's been friends with Mr. Cowell for some time having holidayed with him in St Barts in August last year (along with with hubby Andrew). She also joined Sinitta and Si on holiday in 2011. (credit:Splash)
Lauren Silverman: 9 Facts In 90 Seconds(05 of09)
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5. She's a socialite. You know, like Paris Hilton. (credit:WENN)
Lauren Silverman: 9 Facts In 90 Seconds(06 of09)
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6. She's a dead ringer for Simon's ex fianceé, Mezhgan Hussainy - so much so that even we couldn't initially tell them apart when they all holidayed together last year. Can you? (Mezhgan's in the centre of this pic, Lauren's on the right) (credit:Splash)
Lauren Silverman: 9 Facts In 90 Seconds(07 of09)
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7. Just like Simon, she loves a ciggie, although we're hoping now she's preggers she's kicked the filthy habit. (credit:WENN)
Lauren Silverman: 9 Facts In 90 Seconds(08 of09)
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8. She pretty much knew all there was to know about Simon Cowell before allegedly rubbing belly buttons with him. We know this because she was at the launch party for his *coughs* unauthorised biography, 'Sweet Revenge: The Intimate Life of Simon Cowell' in April 2012. (credit:Getty Images)
Lauren Silverman: 9 Facts In 90 Seconds(09 of09)
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9. She's not to be confused with Laura Silverman (right) who is the actress sister of US comedian Sarah Silverman (left). (credit:Getty Images)