Squirly I know where you are coming from, my ds twins (the eldest in particular) did this around the same age from about 1 year to finally stopping at 18 months, he still does it occassionally. They are now 2.
My poor youngest loves his sleep so would get very bad tempered.
What we did was, first DH would go in, comfort him by stroking his head, talking to him, firmly not forcefully putting him down, tucking him in again. If he woke again I would go in, not speak to him, but stroke his head and tuck him in again. This usually worked, if not we would go in, no talking, no comforting, and just tuck him in. What also worked was only allowing them to sleep 1 1/2 hours maximum during the day (after lunch) and making sure they were not "wound down" too early. They go to bed about 7, sleep about 8 and wake up about 7.30-8am.
It sounds like a palaver, and when you are tired I admit it can be a right pain but persevere (sp?) and it will work out. The biggest problem is if one wakes the other!
Did your twins sleep in the same cot for long? Mine did from birth (in their goldfish bowl at the hospital) until about 8 months. It meant we got some sleep as one would comfort the other! We had to separate when they began fighting for their favourite bit of the bed!