Heaven belongs to Yang. Earth belongs to Yin. The stars belong to Heaven. The ground belongs to Yin. Males, especially the father belong to Heaven. Females, especially the mother, belong to Yin. The palaces or directional sectors therefore would belong to Earth. The stars derived from the house sitting therefore would belong to Heaven. Yin is solid and can be touched. Yang is not solid and cannot be touched. Void and brightness belong to Yang. Solid and darkness belong to Yin. Inside belongs to Yin. Outside belongs to Yang. These are rather classical viewpoints.
How is this used in Ba Zhai? Walls are solid, there is no movement. The Ba Zhai Stars are formless and activated through movement. If we put something unmovable or heavy, like a big cupboard on an inauspicious Star´s sector, then that inauspicious Star becomes suppressed and much less effective. People move and activate the stars. Anything moving will activate the stars too. Doors and windows are more or less void and they definitely are designed to have movement. Moving air or ventilation belongs to that category too. Ventilators, fans, radiators and the like generate movement in the air. We can use all these to activate the Stars.
In the modern day Zeitgeist, there is deemed to be little to no difference between male and female. It is true that there is twilight twice a day, however most of the time there either is dark or there is light. Half of the year is rather warm and the other is rather cold. There still are fixed times of the natural year for sowing and harvesting and the main bulk of food is still generated using the natural cycles of growth and decay. The male principle yet still as always before is inseminating and the female principle is providing the substance for growing the fruit. One can, for political reasons or other, turn that principle upside down. However an exception will remain an exception, generally confirming the general principle or rule. Male belongs to Yang and female belongs to Yin.
Ba Zhai Ming Jing (a book written on the Ba Zhai Feng Shui or the feng Shui of the eight houses) suggests to take the leading male as the reference for harmonising with the sitting Gua of the house. Not the “breadwinner”. If there is no father in the house, according to Ming Jing, the next eldest male should be taken as the reference for harmonising towards the Gua of the house. Only in the case when there is no male at all in the house, only then the mother or eldest females birth year should be taken to harmonise with the sitting Gua of the house. Personally, I agree to this viewpoint. Again I think this philosophy is pretty straightforward by using the principles of Yin Yang. If you wish to apply classical Feng Shui philosophy, why bend it to the whims of any Zeitgeist. After all, you want to use Feng Shui for effect and not fall as a fashion victim.
In the case of a couple belonging to differing groups, like for example the father belongs to the West group and the mother to the East-group, the house Gua should be harmonised with the Ming Gua of the father and the mother should reside in or use the rooms belonging to her auspicious directions.