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, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is not forbidden for you to marry this young man, so we cannot say that you must leave him. However, if he is as you described in the question, then you are strongly advised not to accept him as a husband since he possesses some unsatisfactory qualities that may make the marriage not persist. The Prophet, sallallaahu ‘alayhi wa sallam, urged the Muslim woman to accept the marriage proposal of the pious and well-mannered suitor because such a man generally treasures and values her and fulfills his duties toward her; if he loves her, he will honor her, and if he dislikes her, he will be fair with her.
Since your parents do not approve of this marriage, you are advised to respect their wishes for the sake of dutifulness towards them, especially since parents are often more compassionate to their daughters and more keen to look after their best interest than anyone else. Moreover, it is possible that your parents have asked about this suitor and realized that he is not a suitable husband for you. Moreover, it is advisable for you to forget all about that proposal since his parents would also not allow him to propose to you again because your parents refused his first proposal.
We would like to emphasize our advice to you to forget all about him and to supplicate Allaah much, and to seek a pious husband with the help of your reliable relatives or friends or their husbands. You should know that a Muslim woman is allowed to look for a husband and to offer herself in marriage to him, provided that she observes good Islamic conduct in her interactions with non-Mahram men. This has been underlined in Fatwa 82471.
We would like to point out that it is imperative for a Muslim woman to be careful not to get emotionally involved with a non-Mahram man as this is forbidden in Islam. We have clarified this in Fatwa no. 81356.
Also, it is impermissible for a Muslim woman to get married without the consent of her Wali (legal guardian); if she does so, the marriage contract is invalid. If her Wali unjustly refuses to marry her off to a suitable man (with no valid reason), she may refer her case to a judge in a legitimate Islamic court to investigate the matter. If it is proven that the woman’s Wali unjustly prevents her from marrying a suitable man, the judge is entitled to marry her off himself or appoint a legal guardian for her to marry her off. The Muslim ruler (or judge) is the legal guardian of anyone who has no legal guardian, as established in the authentic Sunnah.
Allaah Knows best.