Will God forgive an unchaste young man who committed adultery, resulting in the woman becoming pregnant and giving birth to a child, when he is remorseful and repentant, yet fears that God may not accept his repentance?

Committing a grave sin does not mean there is no path to repentance, for the door to repentance is open. There must be a firm resolve not to return to disobedience and genuine remorse for it. If the repentance is sincere and true, Allah accepts it and forgives sins, for "the one who repents from sin is like one who has no sin." Allah Almighty says: "And He it is Who accepts repentance from His servants and pardons sins" and "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" Therefore, do not despair of Allah’s mercy, be sincere in your repentance, and increase in supplication, seeking forgiveness, and performing good deeds that wipe away evil deeds.