An ideal cage size for a single adult BRB is 4x2x2... though if you wanted to cut it down in height you could, but I find they appreciate vertical space as well. I wouldn't recommend housing them together. Snakes are solitary animals, they do not enjoy eachothers company and only come together in the wild to breed. You also run into problems monitoring them indivdually, you won't be able to keep track of bowel movements, etc. If someone regurgitattes, you won't know who it belonged to, etc. Also, if one gets sick, so does the other. If you are really set on housing them together, you should IMHO double the floor space like Zoe said to 6x3. The snakes should have enough room that they can avoid eachother all the time if they like. Hope this helped