Bible translators often mistranslate the Greek word
gennao as 'born' when it should be 'begotten'. The single Greek word is used for both begotten and born, so the context should determine which way to translate it.
1 John 3:9 should be (ASV):
(9) Whosoever is begotten of God doeth no sin, because his seed abideth in him: and he cannot sin, because he is begotten of God.
We are begotten by God by the implanting of a seed from God. If the seed remains in us then we have not yet been born, for the seed doesn't remain a seed, it gradually changes into a new creature and is not fully changed until it is born. We are not born as a new creature until our resurrection; until then the seed remains in us as a growing embryo, abiding in our human bodies.
The seed is the word of God. 1 Peter 1:22-23 (ASV):
(22) Seeing ye have purified your souls in your obedience to the truth unto unfeigned love of the brethren, love one another from the heart fervently:
(23) having been begotten again, not of corruptible seed, but of incorruptible, through the word of God, which liveth and abideth {forever}.
i.e. we've not been begotten again with human seed, which leads to a corruptible body which will decay and die, but we have been begotten by an incorruptible seed, the true word of God, that will result in the birth of an incorruptible person.
James 1:18 (KJV):
(18) Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures.
(The KJV translated
gennao correctly as 'begat' in this verse!

)
Having been begotten by the word of truth, Peter says we should purify our souls, obey God's word and truly love our brothers in Christ. It's not an instantaneous change, but an ongoing process - some changing at a faster pace than others.
1 Thessalonians 5 (WEB):
(14) We exhort you, brothers, admonish the disorderly, encourage the faint-hearted, support the weak, be patient toward all.
(15) See that no one returns evil for evil to anyone, but always follow after that which is good, for one another, and for all.
(23) May the God of peace himself sanctify you completely. May your whole spirit, soul, and body be preserved blameless at the coming of our Lord Jesus Christ.
(24) He who calls you is faithful, who will also do it.