Jeff is the middle-aged, kind, father of two. He is mostly bald and what little hair he does have is a mixture of black and gray. He wears a dark blue tie over a white shirt with dark, blue pants. Jeff works in the Elite Forces in the Militarycareer track and wants to be promoted to Astronaut so he can live out his dream to be the first man to walk on Mars.
Jeff and Diane are not in love at the start of the game, however they are at the friendship level. There is a chance card in The Sims that gives Sims a chance to go to Mars. It is only available for Astronauts in the Military career track. It is possible that Jeff passed away before he was promoted into one.
When The Sims was released, Maxis was developing a game called SimMars. It's possible, though speculative, that both Jeff's dream of going to Mars and the chance card for the Astronaut career may be related to that. Likewise, it's possible, though again speculative, that Jeff dying without getting to Mars is a nod to the fact that SimMars was never released.
A different version of Jeff appeared in Japanese copies of the game, with slightly different facial features, but no noticeable graying. His appearance in The Sims for console strongly resembles this version. This version of Jeff starts off Unemployed.
By the time the story-line has caught up to The Sims 2, he and his wife Diane are already deceased. His son, Daniel, marriedMary-Sue Pleasant (néeOldie), and had two children, Angela and Lilith Pleasant. His daughter, Jennifer, married John Burb, and had one child, Lucy Burb. He can be seen in Daniel's, Angela's, Lilith's, Jennifer's, and Lucy's family trees.
Both Jeff and Diane died around the time Angela and Lilith were toddlers and Jennifer was pregnant. Daniel's bio implies that Jeff in fact did not achieve his dream to walk on Mars. It's unknown if he died before or after his wife Diane, as Daniel's memories indicates that Jeff died first, while Jennifer's memories indicates that Diane died first. By the time of his death, Jeff's hair had fully went grey and he still dressed in a white shirt, although one without a tie.
Though his character data was deleted, regenerating him with SimPE is slightly easier than most dead ancestors, as his facial features are almost, if not identical to the 3rd face template, unlike those of most "unresurrectable" Sims. Oddly, according to his SimDNA in SimPE, Jeff's hair was red before it turned grey, despite appearing to have been black in The Sims. According to his age data, he had 30 days left in the elderlife stage when he died.
This Sim has no character data and cannot be resurrected in-game. For more information, read this guide.