Here, Dr. Mike Heiser speak to the question of an "Age of Accountability," for when God sees a person accountable for their sin: https://www.youtube.com/shorts/3v64EYlqDlc
My thought is, while the Bible isn't specific and no certain age is given - which is likely because different people have a differing trajectories of their own spiritual maturity and sin awareness, at varying ages. But what I am certain of is that God is JUST - He doesn't require from people what they are UNABLE to do or understand (repent, commit to Christ, have awareness of their sin), as babies, many youths, or those mentally impaired cannot / are incapable of these. God assigns responsibility for sin - likely, at the point they become aware of it / of Him and are also CAPABLE of responding. The following passage, relating to King David's baby he had with Bathsheba, is one reference to an Age of Accountability. Another reason why a certain age isn't applied for such is that false teachers (especially) might misuse it to mislead people.
2 Samuel 12: 21: Then his servants said to him, “What is this thing that you have done? You fasted and wept for the child while he was alive; but when the child died, you arose and ate food.” 22 He said, “While the child was still alive, I fasted and wept, for I said, ‘Who knows whether the Lord will be gracious to me, that the child may live?’ 23 But now he is dead. Why should I fast? Can I bring him back again? I shall go to him, but he will not return to me.”
Here's more of this from Questions.org: https://www.gotquestions.org/age-of-accountability.html