You'll actually see Captain Antilles at the end of Revenge of the Sith, though I don't think he has any lines, he is mentioned by name by Bail Organa when he puts the droids in his care and instructs him to "have the protocol droid's memory erased".
He is the Rebel captain of the Blockade Runner who gets choked by Darth Vader in the opening moments of Episode IV. Though it's never made clear, it is widely assumed that Captain Antilles is Wedge Antilles' father. Which gives Wedge some motivation to blow up the Death Star since Darth Vader killed his father too.
The real mystery is: who is the "Bail Antilles of Alderaan" mentioned by Captain Panaka in TPM as being nominated to secede Valorum as Chancellor? Maybe Wedge's grandfather?