Forum:Gordon Clegg was born AFTER Betty married Cyril?

I was looking up Betty's marriage to Cyril to see when they got married. The page here has it listed as 1945. When I looked up Gordon Clegg his birthday showed as being in 1950. We know that Gordon was supposed to be the product of an affair that Betty had with a soldier. She gave Gordon to her sister Maggie to raise because she was unmarried, but according to the date of her marriage to Cyril, she would have been married for five years before giving birth to Gordon!

I wonder if this is an actual oversight or if the writers just retconned the storyline when they decided to reveal who Gordon's real mother was?