you can have 2 sims at same active career?

Early on I tried to have two Sims from the same household in the same active career. What happened is both were there, but I could only control one of them. Face/palm.

Well, a lot of it has to do with how many other npc's are available, if you stay late you should see the other sim at some point when the shift change.

You can do that, but you can't play an active work day for both at the same time.
Usually I meet the other Sim at work as a colleague.