A collective billion-dollar multimedia empire before they were old enough to drive, fraternal twins Mary-Kate and Ashley Olsen proved a testament to the value of savvy marketing and keen business management – to say nothing of being downright adorable babies. The sisters made their collective screen debuts in 1987 as seven-month-old infants on the television series, “Full House” (ABC, 1987-1995). Remarkably, their fame only seemed to increase with the cancellation of the show, to the point that by the dawn of their 18th birthdays, tabloids began invading their lives en masse. Reports on