Actress January Jones is still refusing to go public with the identity of her baby boy's mystery father because she insists it's no one's business but her son's. The X-Men: First Class beauty has remained mum on who fathered her 20-month-old child Xander ever since she fell pregnant in 2011, and she's not about to open up now. Jones, who has previously dated Ashton Kutcher, singer Josh Groban and comedian Jason Sudeikis, was asked to name the dad in a recent interview with The New York Times, but she declined, stating: "That's my son's business. It's not the public's business." The star went on to reveal that she was advised early on in her career to keep her private life out of the spotlight - by none other than acting veteran Jack Nicholson - and it's a rule she has stuck by for years. She recalls, "Jack Nicholson once told me: 'You should never give your personal life away, otherwise people will pick you apart. They'll never believe in your character.' "Women should have lots of secrets. It's our right to have secrets. Otherwise, what would we write in our memoirs?" However, Jones has been more forthcoming about her son's little life achievements, telling the publication, "His first word was 'Mama'. His second was 'back', 'cause I kept saying, 'Put it back'."