Are you looking for someone here, at Cafemom, to answer "Yes, I have birthed twins naturally" or are you asking if anyone ever has done it, period?
Yes, twins have been born naturally. And I gave birth to twins who are now 2 1/2 years old, and I did birth them naturally.
I don't know what site Missalissa86 (answer #2) was thinking of but I know the discussion forums at Mothering.com have a multiples forum and the mamas there are very supportive of natural childbirth for twins, and have great track records. Plus lots of informed support for a healthy twin pregnancy, minimizing complications, etc. While I was pregnant, someone there compiled a twin birth video with photos and stats from all the success stories with lots of vaginal births, non-medicated, big healthy babies, etc.
My boys were not huge (basically, two average sized babies) but went to term (born 5 days before their due date) and weighed 7 lbs and 8 lbs
at 10:51 PM on Apr. 10, 2011