Our twins weighed 2.7 and 3.7 lbs and I thought they were small. No comparison here. (they are now 31).
Mine were 7 lbs,11oz and 8 lb 2 oz. Huge in comparison.They are now 8.
I think having twins is easier and better in most ways to having singles, not that there is a lot of choice in the matter. I also have 2 singles, all 4 of my kids are female.