Long-story-short, the child of God I spoke with expressed they were "dumbfounded" over those who choose not to believe that Father, Son, and Holy Spirit are alive and well, lovingly Sovereign over all of creation, and mighty to save even the so-called "worst" of sinners at the faintest sign of true repentance.
I definitely understand that frustration, and our conversation put me in mind of a Daddy's Girl post I shared nearly two years ago in testimony about my own struggles with siblings who have rejected faith in Jesus Christ. Their unbelief (along with that of resolutely unbelieving souls everywhere) is not something God wants us to wrestle with or allow to hinder our continuing witness. Holy Spirit said Abba has a name for the tragic predilection to staunchly reject Christ; please read the post called "Not Understandable" to find out what it is and what Abba says we should do about it.
My heart aches for every child of God reading this today who has unbelieving friends and loved ones in their life they've tried repeatedly to reach with God's light. Please know that - God keeping me - I'll be praying for all of you.
"... fervent in spirit, serving the Lord."