Knowing God's will and not doing them is very dangerous (2 Peter 2:20-21, Luke 12:47).This is because the punishment of disobedience is according to the privileges available to each sinner (Luke 12:41-48,John 9:41,John 15:22).
What are these privileges?
They are the things you know about God,holiness,judgement etc.They are God's commandments (instruction) given to you through the Bible and the Holy Spirit (1 Timothy 3:16).Other means include: words from your brethren (pastors,teachers,parents,etc),Christian articles,Christian movies,gospel songs etc.
How will you know if these other means are of God (1 John 4:1)?
It's easy,God will never contradict His Word.Therefore,study the Holy Bible and pray for the help of the Holy Spirit.

Now that you know the will of God,what do you think the future holds in store for you or that unrepentant member of your family.HARDEN NOT YOUR HEART,the destruction is sudden and without remedy (Proverbs 29:1).
Remember,you have no inkling of what will happen next.
If you find it difficult to obey God,pray to God in faith and discipline yourself (Psalm 119:101).God is faithful,He will make way for you (1 Corinthians 10:13).
Source: https://wetrainchristians./2016/03/15/harden-not-your-heart/