The startling news that Simon Cowell impregnated his good friend's wife is generating headlines around the world.
Relationship experts say Cowell broke a cardinal rule of dating etiquette.
Relationship expert Lissa Coffey said, "You do not date your best friend's spouse."
This isn't the first time a celebrity has dated a best friend's spouse. Actress Denise Richards was widely criticized in 2006 when she started dating Richie Sambora after he split from her good pal Heather Locklear.
Richards got a chilly reception when she talked about the scandal on The View in 2008. She said, "I am going on record, I did not steal Richie Sambora from Heather Locklear. They were on their way to divorce. I understand where people may think differently, I take responsibility of the timing of it."
Shania Twain lived through a similar nightmare in 2008 when she discovered her best friend, Marie Anne Thiebaud, was allegedly having an affair with her husband, music producer, Robert "Mutt" Lange. But Twain had the last laugh when she got together with Marie Anne's ex-husband, Frederic Thiebaud, and married him in 2011.
Experts say Simon Cowell's dating no-no isn't likely to have a happy ending.
Coffey said, "It is always difficult to start a new relationship when you are going in knowing you are hurting someone. This is not the best way to start a relationship."