I used to put one in a sling on the front and the other in a back pack when they were about to sit up. That worked until they got too heavy. There are actual twin carriers but I never saw anyone use one in person. I never could get the hang of two slings at once, though. It felt awkward and off balance, but maybe that's because I'm too short. I don't know. I would recomend slings with no rings for double slinging, I think.