Continuity mistake: While Kramer is explaining about being in the Woody Allen movie, George is in the background looking out the window trying to stop car alarms with his keys. Less then five seconds later, George ends up by Jerry's counter (without being seen) and has a can of Shasta in his hand. (00:08:40)
Continuity mistake: While Kramer is on the phone with the guy who stole Jerry's car, a NY Mets hat is seen upside down on the behind George. When Kramer hands the phone back the hat is now right-side up and facing the camera.
Chosen answer: George does mention his brother in the episode "The Parking Space". They actually really never mention anything that contradicts the fact he had a brother though, it just isn't mentioned.