God gives us the freedom to choose what we ought to. What if we choose not to do it e.g. God calls a married couple to have 5 children but they choose to have only 2?
What are the consequences?
In the “Our Father” we pray thy kingdom come thy will be done. A kingdom has a hierarchy and with God there is a hierarchy of truth or governance as it relates to us. That is as human beings, Adam with all of his preternatural gifts was not like Angels. Adam could not see in depth all the consequences of his sin. That is why we have a chance to be redeemed.
God has a divine will that we strive to manifest in our life like when Jesus in the garden of Gethsemane prayed not my will but Thy will. As imperfect creatures it is true that we fall short of the glory and will and of God, and we should always be ready to repent and align ourselves to the divine will when it is made manifest to us. We know we are always doing the will of God when we are not sinning.
God choose to create a moral universe and by doing so He gave us freewill. That is primary and freewill does not mean we should sin, but because of concupiscence sometimes we do actually sin and that would not be God’s divine will, but God’s permissive will. He permits us to be free, for if He did not then we would be no different than any beast or the grass we step upon as we walk.
If we had two children because we committed a moral sin like abortion then we would lose sanctifying grace and if we died unrepentant then our eternal abode would be hell. If like the God thief on the cross, St. Dimas, we repented then we would be accepted ultimately in Heaven if we died in a state of sanctifying grace.
If we had two children, and sincerely thought that it was all we could bare for a myriad of good reasons, and we were devout in our prayers and sincere of heart, yet God would have given us the grace to have more, it would not be a grave sin, and as tim 2:4 states God will everyone to heaven you would be lifted up on the day of judgement and enter into eternal rest.
God does desire us to be fruitful and multiply, but He also a priori called us to be Spiritual Fathers above natural fathers; thus, communicating God’s life to others.