Jim's whole life seems like a compilation of strange circumstances. Granted, being in the Quarantine is particularly unusual, but he evidently has taken to it well.

"Yes, actually. We did," he nods, gesturing vaguely. "We came from the exact same moment, the exact same place, and just stepped out of the portal together. I asked about that— it's not common, but it's not unheard of either."

It stands to reason that if the portal could bring more than one solid item through at a time, then more than one living being should work much the same way. Provided they come from the same exact point in time and space, from a scientific standpoint, it shouldn't be impossible.