What is the Sharia-prescribed advice given to me after causing problems among my female relatives by relaying كلام (speech) between them, and is it sufficient for me to apologize and ask for their forgiveness?

You have done well with your repentance. You must remain steadfast in it and beware of listening to backbiting (ghibah) and tale-carrying (namimah). Strive to reconcile disputing parties, for there is a great reward in it. The Messenger of Allah (peace and blessings be upon him) said: "Shall I not inform you of something better than the rank of fasting, prayer, and charity?" They said: "Yes, O Messenger of Allah." He said: "Reconciling disputes, for discord among people shaves (destroys good deeds)."