Parents are the psychological guardians of their children. Because parents have been raising their children for decades, children have been relying on their parents for decades, forming a deep-rooted psychological dependence on their parents, which is still the psychological support of their children even after their parents die.
When you encounter difficulties in reality and are under great psychological pressure, you will naturally seek psychological support.
So your subconscious will summon the image of your parents in your dreams and provide you with psychological support.
You dream about your father because your subconscious needs him. When you dream that your father is ill, you know that your father has passed away, so your consciousness modifies your dream and changes your father to be ill.
A bit like the legend of sleeping beauty, the witch cursed death, and the fairy could not completely lift the curse, so she had to sleep instead.
My father changed his face just like my mother because your consciousness noticed that my father had passed away. It is more reasonable to provide psychological support instead of my mother.