(from left) Joan Pletcher, with husband J.J. (center) and stepson Todd (right). (Susie Raisher) Power Broker: Joan Pletcher, Todd’s Stepmother, Rules The Horse Mansion Realm 'saratoga living' sits down with the family matriarch to discuss the real estate business, her Southern upbringing and more. As a military brat—a sort of national emigrant, born into a life of packing up…