Objecting to polygamy

Q: My mother is afflicted with a disease that left her disabled. As a result, she cannot fulfill her marital duties. My father sought treatment for her inside as well as outside the Kingdom but to no avail, which led him to marry another woman to keep himself chaste. (Part No. 19; Page No. 186) He is a healthy man, all praise be to Allah. As his sons, we approve of his marriage as long as our mother is still his wife and lives among us. One day, my maternal aunt came to visit and asked to take my mother (her sister) to live with her for a month for the purpose of treatment. After the month, my aunt was informed of my father's marriage and when we asked her to return my mother since her condition had not changed, she absolutely refused. My maternal aunt and some of my uncles were against my father's marriage to another woman. When we asked her about the reasons of her disapproval, she said that my father would better commit Zina (sexual intercourse outside marriage) and not marry another woman, for then he would be accountable for his sins. Some of my uncles said that if things were the other way round, my mother would not have the right to ask for divorce to marry another man. I would like to note that we brought our mother by force, fearing that my father would divorce her. During the course of the dispute with my aunt and uncles, I raised my hand to slap my aunt but I sought refuge with Allah (Exalted be He) from Satan and I did not do it, all praise be to Allah. Now we live happily and contentedly with my mother. One week after the dispute, I went to my aunt to apologize to her and to keep my ties with her but she refused to answer my greeting. Two weeks later, (Part No. 19; Page No. 187) I visited her again and she received me coldly. It is worth mentioning that I live in the city of Baqiq. My aunt and uncles stopped visiting us in our house except when I take my mother to the other house which is in Al-Ahsa'. I live with my father and brothers in the same house in Baqiq, while my aunt and uncles live in Al-Ahsa'. I have another house near them in Al-Ahsa' in which I stay for three days each month. My aunt would come and visit my mother alone and stay for half an hour or more with her before she would leave. As for my uncles who were against my father's marriage, they have not seen my mother for a whole year now while others visit her every month or two. I want to stress that my aunt does not visit us in our house in Baqiq and if we do not go to the other house for a while, she does not see her sister all this time. Before, she used to come every two or three weeks to visit us. I hope your Eminence would answer my following questions:1.As their nephews, what is our stance toward our aunt and uncles? Now, they do not like my father at all, should my brothers and I keep our ties with them or sever them until they solve their problem with our father? To be honest, my father has not asked us to sever our ties with them, on the contrary, he urges me to visit them. However, they do not respect my father and when I visit them, they do not welcome me (Part No. 19; Page No. 188) heartily and lovingly. I have tried to make peace between my aunt and uncles and my father to regain our previous relations but nothing has changed.2.What is the ruling on marrying four women? When is it permissible for a Muslim to marry four women? 3.What is the punishment for someone who urges or advises others to commit Zina in order not to marry another wife, may Allah save us?4.What is ruling on my aunt and uncles' stance in this whole matter? Is their response to my father's marriage right or wrong?