Matthew Broderick's 11-year-marriage to Sarah Jessica Parker could be on the rocks after explosive details emerged of his affair with a 25-year-old redhead. Matthew, 46, had trysts with the sexy youth counsellor at her apartment in New York's Upper East Side, and at the home of one of Matthew's own celeb pals, according to the latest issue of Star magazine. The couple became so close that the girl even had a nickname for Matthew - "Matty Cakes". And the report says on one occasion, Matthew grabbed the girl and kissed her passionately on the lips, before leading her upstairs to have passionate sex with her... Phew! Talk about sex in the city! According to Star the girl - who hasn't been ID'd - ditched Matty when he lied to her about where he was spending his Christmas vacation - in Hawaii with Sarah and his son, and not in Ireland alone as he'd told her. Matthew's rep declined to comment to Star about the claims of Matthew's cheating.