This just keeps getting better and better because it's making me come up with some wild guesses to where this is heading. After watching Father Knows Best, I'm going to take another leap here and say that Rudy and Dexter are Half-Brothers. Why? Glad ya asked. So Dexter gets a notice to identify the body of Joe Driscoll, who turns out to be his biological father. It's later revealed (implied) that he may have been injected a lethal dose of drugs to make it appear that he had a heart attack. We the viewer know that this is the case because we see Rudy going back to "get rid" of the witness that can identify him being at Joe's place the week before. Okay, that' doesn't explain how they are half-brothers.

My rationale is that Rudy is the son of Joe, and has always known about Dexter and has now sought him out because they both share that Serial Killer DNA. It's the only thing that explain how he knows about Dexter, where he lives and the fact that he knew about Joe being his father to the point of killing him to set up a meeting of the two, by way of his sister Deb. It's a stretch, I know. But it''s plausible and something I can see the writers coming up with for that ultimate Season Finale twist.