Hi there, and congratulations!
Our two shared a normal sized cot until they were about 7 months old - they weren't big though, were still under 5lb each when they came home from scbu. To start with, we tucked them under the same blanket, then next to each other, then top and tail.
When they went into separate cots, they were in an L shape - the only way they'd fit in the room. When we moved, we put the cots next to each other- but I'm not sure I'd advise this - around the age of 18 months they'd start somersalting into each other's cots! Head first, very scary. Aged 2ish they went into beds - to stop the somersalting - and they share a room.
hth Carolinex