I love to keep it simple:
“But as many as received Him to them gave He the power to become the children of God, even to them that believe on His name.” (John 1:12)
“For God sent not His Son into the world to condemn the world; but that the world through Him might be saved.” (John 3:17)
Jesus said: “It is the Spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.” (John 6:63)
“He[God] hath made Him[Jesus]to be sin for us, who knew no sin that we might be made the righteousness of God in Him.” (2 Corinthians 5:21)
“Being confident of this very thing, that He which hath begun a good work in you will perform it until the day of Jesus Christ.” (Philippians 1:6)
“And this is the record, that God hath given to us eternal life, and this life is in His Son. He that hath the Son hath life; and he that hath not life.” (1 John 5:11-12)
“For whosoever shall call upon the name of the Lord shall be saved.” (Romans 10: 13)
Only those who have received Him are God's children. The rest are simply God's creation in His image. He loves them, but until they are saved, they are NOT God's children and have no inheritance in God's Kingdom.