In addition to writing and producing songs for Shania Twain, Robert John "Mutt" Lange earned a hit in the 1990s as the writer of BlackHawk’s single "I’m Not Strong Enough To Say No." But Mutt insists he is indeed capable of saying no and denies a report that his split with Shania is the result of an affair.

People magazine reported that their separation, announced last week, came about only after Mutt began a relationship with their assistant, Marie Ann Thiebaud.

But Mutt told the magazine there was — and is — no affair, that he and Shania were "literally just growing apart." Shania, the mag claims, is "devastated" over their parting, and that it "came out of left field."

The couple married in December 1993, and have a son, Eja, born in 2001. Shania’s career took off after she began working with Mutt, who had already built a career before they met as a writer and producer for such pop and rock acts as Foreigner, Bryan Adams, AC/DC, the Cars, Billy Ocean and Huey Lewis & The News.