All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If the reality is as you mentioned that your father and brother curse you, speak ill of you and break the relations with you, then this is a trial for you. You have to be patient with them as this is how a believing man and woman should be. The Prophet said: "How wonderful is the case of a believer for there is good in every affair of his and this is not the case with anyone else except the believer. If he is blessed with prosperity, he thanks Allaah, and that is good for him, and if he is afflicted, he endures it patiently and that is good for him." [Muslim]
So, you have to be patient and attempt strenuously to correct the situation. You have to seek the Help of Allaah and then the good influential people to convince your father and brother that your refusal to inform them your husband's personal matters is appropriate, because he may dislike it and it may even cause you harm. May Allaah guide them to correct themselves.
As long as you did not violate your father's right you will not be sinful and Allaah will reward you for concealing your husband's secretes. As for your brother's behavior i.e. coming to your house and cursing you, it is wrong and your husband has to prevent him from that except if he fears a greater harm.
A Muslim saying: 'Allaah will never forgive him' is a daring statement on behalf of Allaah, so, it should be shunned.
The Prophet stated that a person said: "Allaah would not forgive such a person. Thereupon, Allaah the Exalted and Glorious, said: Who is he who adjures about Me that I would not grant pardon to so and so; I have granted pardon to so and so and blotted out your deeds (who took an oath that I would not grant pardon to him)." [Muslim]
Allaah Knows best.