Sources close to Katharine and Nick tell TMZ ... the two have been separated for 6 months and are living apart. They were married in 2008. It's unclear where Michael's relationship with Mary stands -- but it seems it's also on the ropes, because over the weekend he was sucking face with Katharine in broad daylight in L.A. like he didn't care who saw.  The two weren't shy with the PDA either -- holding hands and cuddling each other in Hollywood.