Hello! My kids are 2.5 years apart and started sharing when my dd was ready to be in a big girl bed. We invested in the Matrix beds. They are pricey but they're great for versatility. I started with them in two separate single beds then when my ds was old enough I bought the bunk package which allowed us to make them into bunks. I LOVE these beds as you can put them in so many different ways. What I love about this is that when the time comes to separate them you can without buying another bes. Here is the website if you want to take a look http://www.maxtrixkids.com/
But brace yourself as they are much more expensive than any other bed set but you only have to buy once. My kids absolutely love them. Good luck!
