I have 15 month old boy/girl twins. Instead of using two bassinets when they were first born, I put them together in one full-size crib (at the foot of my bed). They slept together in the same crib for 6 months (we had moved them to the nursery at this point). They slept with their head & feet going the wrong way in the crib (side to side instead of length wise). So when they got too long to fit in that direction, we separated them into the two cribs (which were side by side in the room). Unfortunately, at 8 months old, they started teething (my boy especially) and waking up at night. My husband pressured me to separate them into two rooms to avoid them waking each other. They are 15 months old now, and still in separate rooms. I feel very torn about this b/c I hear so many sweet stories about twins sharing a room. But my boy was a TERRIBLE night sleeper from months 8 to 13. Now he is back to sleeping through the night (thank goodness!), but I am not sure how to re-introduce them to the same room at this point....so most likely just going to keep them separate.
Best of luck!! Twins are such a special experience :)