From writer/director Derek Cianfrance and based on the award-winning novel of the same name by Wally Lamb, the six-part HBO limited series I Know This Much Is True follows identical twin brothers Dominick and Thomas Birdsey (played in two stand-out performances by Mark Ruffalo) on their very different life paths. It’s a family saga of sacrifice and forgiveness that begins in their present in the early 1990s and digs into different stages in their lives, as it highlights how mental illness affects everyone, including the one directly suffering with it. During the virtual press day …