Matt Winkelmeyer/Getty Images Hilary Duff is mourning the loss of her Lizzie McGuire costar, Robert Carradine. "This one hurts. It's really hard to face this reality about an old friend," Duff, 38, wrote via Instagram early Tuesday, February 24, alongside throwback photos with her former on-screen dad. "There was so much warmth in the McGuire family and I always felt so cared for by my on-screen parents. I'll be forever grateful for that. I'm deeply sad to learn Bobby was suffering. My heart aches for him , his family, and everyone who loved him.