Trivia: Michael C. Hall and Jennifer Carpenter, who play siblings on the show, were actually married in real life, from 2008 - 2011.
Trivia: In this show, Christian Camargo plays Dexter's older brother. In real life, Michael C. Hall is 5 months older than Camargo.
Answer: No, Harry is not the real father. While he did have an affair with Dexter's biological mother (Laura Moser), this was when she was his C.I. Dexter was already born at that point.