(S02E06) A couple of commenters last week mentioned they thought Harry could possibly be Dexter's biological father. Someone else mentioned that Dexter actually had a blood test done to prove who his father was, and I seem to remember that myself as well, though for some reason I can't remember the details.

In any case, Dexter continues to question how honest Harry had been with him when he was alive. In fact, he's getting pretty angry at him. It seems to me that, along with Lila's influence (whether positive or negative), Dexter not trusting what Harry taught him is just going to cause Dex to become even more sloppy.