I breastfed mine, and one after the other because I found it too difficult and not at all pleasant to feed them simultaneously. With my elder boys I gave them the occasional bottle, but when I found out I was having twins I threw out all my bottles so I wouldn't be tempted to use them. I knew in the early days it would be hard but in the long run I find breastfeeding so much easier. As it happened my boytwin was ill so had some formula in hospital in addition to EBM and it never agreed with him (he is allergic to cows milk protein) so I breastfed them both to 22 months.