Answer
Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother in Islam, it gives us pleasure to receive your question and to see Muslim youth interested in knowing the teachings of Islam, which Allah has chosen for His servants as a way of life. A true Muslim should refer to scholars to get himself well-acquainted with the sound image of Islam.
In response to your question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states,
In Islam, marriage is based on the free choice of both partners, i.e., the man and woman. But at the same time, they should exercise this choice with due consent and approval of their parents. Nevertheless, it is ultimately up to them to decide whom to marry so long as they are religiously compatible.
If there is no issue of compatibility involved, then your parents have no right to object to your marriage. You should, therefore, communicate your desire to get married to your parents and her parents. If you cannot do it by yourself, then try to do it through wise people in the community who are respected for their wisdom and knowledge.
According to the teachings of Islam, if your cousin does not agree to marry your older brother, the marriage cannot take place. We learn from authentic reports that once a woman complained to the Prophet (peace and blessings be upon him) that her father had given her away in marriage to a man without obtaining her consent, and upon ascertaining the truth of her statement, the Prophet (peace and blessings be upon him) ordered the annulment of the marriage; but then the woman said to him, ‘I have accepted my father’s choice, but I wanted to let women know that no one can force them to accept anyone they don’t like as a marriage partner.’
So it is up to both of you to stand up for your rights and let your parents know.
Excerpted, with slight modifications, from: www.islam.ca
The eminent Muslim scholar, Dr. `Abdel-Fattah Idrees, Professor of Comparative Jurisprudence at Al-Azhar Univ., adds,
Taking the permission of one’s parents to marry a particular woman is not obligatory in Islam if the man is sane and has reached puberty. So if a man is sane and of age, and wishes to marry a woman whom he sees to be good and righteous, then he has the right to marry her even though his parents disagree with the marriage. But he must respect his parents and clarify his point of view regarding this marriage. This is to prevent severing family ties.
Allah Almighty knows best.