Who is Kristin Cavallari’s mystery man? After the Laguna Beach star debuted her relationship with new boyfriend Mark Estes on February 27 via an Instagram post, many have been curious about the 24-year-old hunk. Cavallari was previously married to Jay Cutler — with whom she shares kids Camden, Jaxon and Saylor — before calling it quits in 2020. The blonde beauty has not had a serious public relationship until Estes came along. According to a source, Estes and Cavallari first communicated online before they connected face to face. “They’ve been dating longer than people think and have kept it v…