"They were both very much looking forward to appearing in the show, but Sharon's focus now has to be on the family and, more importantly, Aimee's health," read a statement from their publicist.
"They apologize profusely for letting the cast down and wish them all the very best for the upcoming production. They hope everyone understands and would be very grateful for privacy at this sensitive and difficult time for them."
No other details were disclosed about the condition of Aimee, who is the daughter of rocker Ozzy Osbourne.
DISCUSS AND COMMENT ON THIS STORY Reality TV World now offers Facebook Comments on our stories. To post a comment, log into Facebook and then 'Add' your comment. To report spam or abuse, click the 'X' in the upper right corner of the comment box.