"Yeah, the one in my universe. Other-Steve." His mouth twitches a bit into half a smile. "This Steve comes from earlier in the timeline, well before the time-traveling became a thing. He spent ten years on the Barge, it-- changed him. Like ten years anywhere would, really. We prevented the thing they needed time-travel for in his universe, and faked his death so he could stay with me and the version of me in his universe got some decent closure."

Yes, multiple universes are awful. And also another reason why he isn't so sure about his deal anymore.