The “OC’s” hot mama, Kelly Rowan, has struck romantic paydirt, we hear. After dating for three months, the actress, 41, has moved into the Toronto mansion of Canada’s richest man, David Thomson. Forbes ranks Thomson, 50, as the 10th-richest person in the world. Among his estimated $20 billion in assets is the recently acquired Reuters. Last year, he stunned his second wife, Laurie Ludwick, by serving her divorce papers hours after she checked out of the hospital where she’d given birth to their son. A source says “his teenage daughters aren’t thrilled” by the new romance with Rowan, whose rep confirmed they’re an item. Thomson’s rep didn’t return calls.