The Hot Tub - S7-E5
Plot hole: When Elaine is searching for Jean Paul in the streets, one of her verbal flashbacks is of Jean Paul saying, "I trust Elaine, she is my friend." However, Jean Paul made this remark to Jerry, and Elaine was not there to hear it. How could she have a flashback of it?
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.