We advise having separate sleeping areas for littermates. This can firstly help to minimize separation anxiety and allow them to have confidence in themselves. They can nap together during the day but at night we advise crate training and even having them in separate rooms if possible. By crate training them to their own crate, you should be able to easily encourage them to go to bed in their own crates. If possible, do it during their younger years so they do not struggle at an older age wondering where to sleep or why you need to separate them.