Regarding the question, we would like to quote Dr. `Abd al-Fattah Idris, professor of Islamic jurisprudence in Al-Azhar University, who said,

Wilayah (guardianship) in marriage is a right by which the wali (guardian) shares with the woman under his guardianship the responsibility of choosing the suitable life partner for her. However, in all circumstances he does not have the right to force her to marry a person she does not agree to. He also does not have the right of preventing her from marrying the one she wants to spend her life with just because he does not like him. In case he obstinately refuses a suitable person whom she thinks to be good for her, the right of wilayah goes to the next one in order; in this case one of your full brothers. This is because your father has no legitimate reason to prevent your marriage as long as your cousin in a suitable person for you.

So, one of your grown brothers should share this responsibility with you. Since you are a grown person, the lawgiver has given you the right to choose your husband. During the time of the Prophet (peace and blessings be upon him) a woman came to him and told him that her father wanted to marry her to his nephew and she was displeased with that. The Prophet (peace and blessings be upon him) suspended her marriage and gave her the right to decide. She said: O Messenger of Allah, I approve what my father has done, but I just intended to inform women that men have nothing in this affair of theirs.

This is clear evidence that it is the woman that has the first opinion with regard to her marriage, not her father or any other relative, as long as the person she chooses is suitable and religious. The Prophet (peace and blessings be upon him) said, “When a man with whose manners and religiosity you are pleased comes to you [seeking marriage] accept his marriage proposal; if you do not do so, there will be mischief in land and a broad corruption.”

Note: The right of wilayah goes to the brother or the paternal uncle in case of the father unjustifiable refusal. In case, there is no such relative available, you may resort to the Islamic court in your country, or the Islamic center in there is no such court.

We would like also to remind you that you should be always kind and dutiful to your parents and to regard this as necessary measures that you take out of necessity. Try to seek the help of other relatives or people of influence on your parents who may change their attitudes. May Allah guide you to the best.