"Starting off the year with a new fiancé, @bluehamilton," Dallas tweeted Sunday, along with a picture of Hamilton. "A great way to kick off 2013!"
Hamilton is a singer/songwriter based in Los Angeles. He and Dallas have been dating since 2009, according to Us Weekly, but this is the first time they've acknowledged their relationship publicly.
Dallas starred as the title character in ABC Family's Kyle XY from 2006 to 2009.