Showbiz
The reality show judge appeared on Oprah Winfrey's chatshow with X Factor winner Leona Lewis and told Amy and Randy Stoen that he would be their daughter Madelaine's "guardian angel".
The three-year-old was recently diagnosed with cancer and Cowell said he would help ease Amy and Randy's financial worries.
"I didn't know what to do in this situation other than to do something which I hope will help your situation. I know you are having problems with your mortgage. As of this afternoon, your mortgage has been paid off," Cowell said to a tearful Amy.
The Stoens have been travelling 100 miles from their home in Minnesota each day so Madelaine can receive life-saving treatments.
Cowell later admitted: "I never knew doing good could feel so good."
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