Alexis Houston, Whitney's half-sister, denies she is Matt Lauer's mistress

matt-lauer-alexis-houston.jpgThe details just keep getting juicier. It has come to light that "Today" host Matt Lauer might have been cheating on his wife of 11 years, model Annette Roque -- possibly as recently as at the 2010 Vancouver Winter Olympics.

Now Hollyscoop says his mistress is Alexis Houston, half-sister to recording artist Whitney Houston. A source close to Matt's camp tells them that Alexis and Matt met on the set of "Today" back in 2007 when Alexis accompanied singer Dionne Warwick to the show.

"There was some tension with Dionne and the producers before the show went live and Alexis smoothed out the drama, which caught Matt's attention," the source says.