Joe very frequently brings up his brother Jeff on the show, leading Lars to suspect that the former is attempting to subtly shoehorn him into the podcast. On earlier episodes, Lars would emphatically interrupt any attempts by Joe to bring him up by shouting, "Stop trying to make Jeff happen on the podcast!"
Jeff's voice has been described as "Joe with a frog in his throat". He apparently shows no interest in the podcast, but accepts his brother's commitment to it and leaves him to record in peace once a week.
In late 2019, Joe and Jeff got an apartment together.