What is the ruling on breaking off an engagement due to the girl's lack of beauty and the incompatibility of the two families' social statuses after performing الاستخارة (istikharah, prayer for guidance) and giving initial approval, and does the suitor bear a sin for breaking off the engagement?

The girl has no right over the suitor as long as the matter has not gone beyond the engagement. The engagement is merely a promise of marriage and it is permissible to break it. The brother's breaking off of his engagement was due to a valid reason, which was his compliance with his family, and this is commendable, even obligatory if one or both parents insist on it. It should be noted, however, that it is not permissible for parents or anyone else to prevent a son from marrying whomever he wishes, unless there is a legitimate religious reason for it, for the Sharia (definition) has guaranteed a man the right to choose his wife. Allah Almighty says: "Then marry such women as seem good to you," and Allah Almighty says: "Indeed, the most noble of you in the sight of Allah is the most righteous of you." The Messenger of Allah, peace and blessings be upon him, said: "Indeed, there is no superiority for an Arab over a non-Arab, nor for a non-Arab over an Arab, nor for a white person over a black person, nor for a black person over a white person, except by piety. Indeed, the most noble of you in the sight of Allah is the most righteous of you."

The questioner should inform his family that preventing his brother from marrying is not permissible. If the objection is from other than the parents, then their obedience is not obligatory. However, if the objection is from the parents or one of them, then the brother must turn away from marrying her, because obedience to parents is obligatory, unless the brother fears falling into sin due to his inclination towards the girl, in which case he may marry her and must appease his parents.