Before becoming a busy mom to sons Braydon, 4, and Mason, 6, Hart starred as insightful teen Clarissa Darling on Clarissa Explains It All and Sabrina Sawyer on Sabrina the Teenage Witch. Now, the actress, 36, is expecting her third child with hubby Mark Wilkerson. "(Early) Happy Birthday to me! And baby makes 3!" she Tweeted April 17.