If you are housetraining them or if there is any chance they will not get along they should have separate crates. If they are already house trained and the crate is just for when you leave the house, and they get along well, you can get one crate but make sure it is large enough. Mine had separate wire crates until Sam was finally trained and now they have one very large crate that they can share. They will let you know if they want to be separated.
