Should a person proposing to an engaged woman make Kaffarah?

Q: I betrothed one of my sons to my nephew's daughter. Her father agreed but delayed the conclusion of the marriage for some time. I traveled to Riyadh for twenty days and before returning home, another suitor proposed to her (Part No. 18; Page No. 54) and her father agreed even though I am his uncle. I am not sure about this engagement and I am waiting for the date her father appointed to conclude her marriage to my son. Your Excellence, it is known that among the conditions of engagement is that a person should not engage a woman who is already engaged. We hope Your Excellence would tell us whether it is permissible to engage a woman who is already engaged to someone else. What are the consequences of doing this? May Allah safeguard you and guide you to all good.

A: It is not permissible for a Muslim to engage a woman who is already engaged to someone else. It was authentically reported on the authority of Ibn `Umar (may Allah be pleased with him and his father) who narrated that the Prophet (peace be upon him) said: "None of you should make an engagement proposal over the proposal of his brother.” (Agreed upon by Al-Bukhari and Muslim) (Part No. 18; Page No. 55) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.