Sometimes God puts it strongly upon our hearts to change the hearts of others through prayer. This post on Broadbent's blog shows us the miraculous power of our prayers on others. Do not give up hope if God has placed it upon your heart for him to make a change in someone.
https://markbroadbent.org/2014/08/11/our-prayers-can-get-god-to-override-free-will/
https://markbroadbent.org/2014/08/11/our-prayers-can-get-god-to-override-free-will/
