Do You Take Dexter Morgan? - S3-E12
Other mistake: The marriage certificate for Rita's first marriage shows her date of birth as 04-19-1989 and Dexter states she married at 16. The marriage date is 08-16-1989, when she would have been 4 months old. She also would only be 17 at the start of the series (2006) if she was born in 1989. (00:13:45)
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.