Katie Waissel's family are "completely shocked" by the actions of the X Factor contestant's 81-year-old grandmother after it emerged she is working as a prostitute and porn star.
Further revelations are expected after a spokeswoman for PR guru Max Clifford confirmed Sheila Vogel was a client and said she had been "inundated" with media offers.
Katie's sister Natalie Davis, speaking to the Press Association on behalf of her immediate family, said: "We were completely shocked and devastated to hear of the news that my grandmother, Sheila Vogel, has been conducting immoral activities, including prostitution and pornography.
"We, as a family, disassociate ourselves wholly from these activities and from any future stories that arise from them. It is a personal family matter and we would ask that during this difficult time we are allowed space to deal with it as a family. There will be no further comment."
The revelations about her grandmother come as another blow for Katie, who has divided fans' opinions since her first appearance on the ITV1 talent show.
A spokeswoman for Max Clifford said: "Sheila is a delightful woman. She has been inundated with media offers which are all being considered.
"One thing she wants to make clear is that what she does is nothing to do with Katie."
A clip from a porn film, starring Mrs Vogel under the name Cecilia Bird, will be shown on adult channel Red Hot 40+ next Saturday.