I would give them an option
Get each of them a crate for alone time but also get a large ex-pen with two beds. If they want, they can stay together. In my home, I have one large crate for each of my kids. It's like their room and they can go freely in and out. They usually will not go into another's crate.
At my boyfriend's, they are not allowed to have free run of the house at night. I have two really large ex-pens set up. The two girls stay together and the two boys stay together. I have two beds in each ex-pen. They do very well and love to snuggle. This way they keep each other company.
Now, the question is what will I do if we ever move in together. I love sleeping with my kids but he only lets me take one to bed at his place. So I say, if he moves in with me .. I set the rules and if I move in with him..I have to live by his rules. Luckily, it looks like he will be moving in with me