i dont have twins but i think it is a must. new born is still ok to sleep together in one cot as their movement is limited, however, they are going to turn around 3 months and that causes dangerous.
yes buy 2. I don't think 1 works well, yes, when they are small, 1 cot OK. but when they are 6 mos, cannot fit into 1 cot. So at that time, u'll have to buy another and don't forget, u have 2 bbs at home & u're already v busy. And u have to buy again, assemble...