Hi! My neighbour has 3mo twins and we were just talking about this today. She FF them at different times, demand feeding both of them. She tried to feed them at the same time, thinking it would be easier, but it turned out to be harder for her cause one would be hungry, and the other wouldn't, so she would feed one, then try to feed the other, have them not hungry so they didn't have it, and then she would just have to feed them again later when they were hungry. She said it works so much easier for her to just feed them whenever they are hungry on demand, but it is usually always within the same hour. Plus I imagine it would give her time to feed one, then spend time settling them etc before moving on to the next baby, as opposed to having them both fed together then needing to settle them together kwim?

I think you'll find though that no matter how you do it, they wont' know that you want to feed them every 3hrs, so whichever method you choose to feed them, it's best to follow their cues.