What is the solution for a young man who wishes to propose to a girl two years his senior, but his family has found out that there is another person who intends to propose to her but has not yet approached her family?

There is no impediment to proposing to a woman who has not assented to another suitor, for a mere proposal or the intention of it does not prevent another proposal. The Prophet's prohibition: "A man must not propose over the proposal of his brother," refers to a situation where the woman has assented to her suitor and they have become close. However, if she has already assented, then it is not permissible to propose to her.