I wonder what denomination they were brought up in?
You are correct. The natural man,mind,is also the carnal man. Those who are unable to understand the things of God because we are first separated from God due to our human ,fleshly,nature.
1 Corinthians 2:14
The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
When God enters in by his grace and opens our consciousness to faith and the understanding the things of God,that is when we are eternally in His irrevocable Salvation. Indwelt by His Spirit.
Job 32:8
But it is the spirit in man, the breath of the Almighty, that makes him understand.
The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
1 Corinthians 2:14