In The Itchy Brain Simulation", Leonard mentions his aunt that knitted him a red sweater with "Lenny" on the chest in white letters. It was made of yarn that was very irritating and it made Leonard scratch it when he wore it. Sheldon made Leonard wear it until he returned a DVD to demonstrated how something gets into his brain causing an itch that stays there until it is resolved.
- Brother or ex-brother-in-law: Alfred Hofstadter
- Sister or ex-sister-in-law: Beverly Hofstadter
- Nephews: Leonard Hofstadter, Michael Hofstadter
- Niece: Unnamed
- Niece-in-Law: Penny Hofstadter née ?
- Niece-in-Law: Unnamed
- Nephew-in-Law: Unnamed
- Possible Father: Unnamed
- Possible Mother: Unnamed
- Possible Brother: Floyd
- Possible Sisters: Edna, Nancy
- Possible Children: Unnamed