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Michael C. Hall and Jennifer Carpenter, Dexter
As if Dexter's incestuous story line wasn't uncomfortable enough, consider the fact that these on-screen siblings used to be married! Hall and Carpenter eloped on New Year's Eve 2008 but separated two years later. Though they may no longer be an item in real life, the exes recently shared one of the most cringe-worthy romances when Deb (Carpenter) developed feelings for her — thankfully adopted — brother Dexter (Hall).