Is it permissible for me to wait for a young man who proposed marriage to me but is still studying and has not yet proposed to my father, knowing that my relationship is limited to his mother and sister?

If the suitor is a man of religion and good character, there is no harm in the woman waiting for him to marry, as long as she is not negatively affected by it. Betrothal is prescribed for marriage, and it is better for whoever is able to marry to hasten it and not delay it. It must be noted that the suitor is a stranger to his fiancée until he concludes the marriage contract with her.