My mother always told me that there was not much money at home, but she always stuffed a lot of money into my uncle's house. How should I understand it?

This is called robbing Peter to pay Paul. You'd better discuss this with your father and have a family meeting. If you go on like that, you will run out of savings at home, and once you need emergency, you will become a cook without rice. After all, your uncle is an adult, so there is no need for your mother to raise him, even if he is a concubine. Now it is also economically independent, and the family is separated, which is far from the same.