If the room is small, bunk bed is the best answer to go for in the sibling rooms.
It is also so much fun to sleep in one, whether on top or bottom...
For some countries it is totally normal and almost a must to have soil and grass on top of the roof, with very valid reasons. However for some warmer climate countries, it is quite strange and very interesting to see such buildings.
No matter what, it is so useful and so cool!
Rocking chairs and swings are fun, right?
How about a bed that swings?
Even when it's very little, since it will be securely fixed to the ceiling; would you find it amusing?
Isn't it always preffered to rest indoors while the weather is rather cold?
Design is the Salt X Pepper of life. It is not a must, but if you have it, then you have the appetite for life.