Bottles for twins

Twins burn through bottles at a rate that surprises everyone, so the answer is two of everything, and then some. The realistic starting fleet is eight to twelve bottles, because the alternative is washing bottles at every feed, and you will be doing enough washing as it is. Start small with one or two brands, though: babies veto bottles, and twins veto independently.

Used bottles are fine after sterilization, but nipples are always new, no exceptions: they degrade in ways you cannot see and they are cheap to replace. Whatever brand wins, buy the matching parts in bulk and standardize. A drawer of mixed bottle systems is a nightly logic puzzle you do not need.