Kris Jenner's sister has alleged the star cheated on Bruce Jenner in the wake of their announcement that they are separating.

Karen Houghton alleges 57-year-old Kris confessed to her that she'd had an affair during her 22-year marriage to the former Olympic athletics champion, telling Star magazine: 'Kris has admitted to cheating. It's so funny because I could never see a guy cheating on her. She's so powerful.'

Karen believes Bruce has been faithful throughout their relationship, and although the pair have insisted they are not getting a divorce Karen thinks her sibling will move on a lot faster than her husband, saying: 'I do not believe that [he] has ever cheated on Kris ... And I don't think he ever will, if they stay together. Bruce will find someone else. But I guarantee you, Kris will find someone in two days. I promise!'

Karen thinks Kris has a 'hole in her' and doesn't think she is entirely happy which is why she spends her time working as a manager for her children, saying: 'My sister is a person who likes to stay really busy, focused, in control, done, done, ABC, you know. And even a little bit anal. But I think that's because when you have situations inside of you that aren't filling your complete happiness, there's a hole in you. And I think right now, Kris has that hole in her because of what's going on with the family right now.'

Kris meanwhile is denying her sister's accusations, insisting she is no longer in touch with her sister Karen telling RadarOnline: 'Unfortunately, my sister has been dealing with demons for years. I am not in touch with her but I wish her the very best.'

Sources (i.e. Kris Jenner's horse whisperers) claim the siblings haven't seen each other for nearly a year and Karen has no real knowledge about Kris' personal life, with 'a source' saying: 'The reality is that Karen and Kris have not had a discussion about Kris' private life for 28 years. She has no knowledge of Kris' family life or her husband, except what she sees on the show. And she has used this to create a fanciful tale of what is going on inside the family. Karen has a tendency to be angry and jealous and perhaps this was her motivation to go on the media tour.'