San Diego Sheriffs are joined by the FBI in the continued search for clues to explain the mysterious vanishing of a vibrant, successful couple and their two young sons. Joseph and Summer McStay, along with their two sons, Gianni and Joey were last seen Feb. 4, 2010, in Fallbrook, Calif. Authorities say they have real concerns for the family's safety but still have no answers, leaving many questions as to what could have happened.