Five characters apartment

While new buildings are mostly designed with some visual concept behind it, renovations are by large extent driven by restrictions. The latest apartment remake only has one such limit and one simple goal. Make an apartment for a family of 5 within the available space with 4 existing windows, which are to be unchanged.

The spaces should then be as follows, the main bedroom, three youth rooms, living space with a kitchen and a bathroom. The only way to divide the incoming sunlight is to use some of the windows for more than a single room. Or is it?