I saw a thread in the past week or so about an alarming high percentage of abortions in NYC. I'm fairly certain the percentage would have far outweighed parents simply not planning to have children and as such not conceiving them. Yes I remember seeing family gatherings and some living hand to mouth existences due to large families the dad could not support. And I'm talking 1960's here and the men were willing to work. I also saw 9 kids suffer because the father refused to buy groceries and bought beer instead. I even saw Mr Deacon next door to them ask them to go to church every Sunday but refused the woman and kids water from his well as they had none so my family provided it instead.
I am the youngest surviving male to carry my grandfathers name. I am the only surviving male to carry my dads name. The only others is an uncle and a cousin who died. I did not have kids because there was a higher calling and need in my life at the time so my grandfather and dads male bloodline is finished. Yes I do think I did GOD's will. I don't think it was a sin I had no kids with my genes. It was because of what happened in life. We made a choice not to have a kid together and it took a lot of thinking to do so.
But as for your point here's mine. If the good Lord wants a lot more persons on earth he himself can produce them from rocks can he not? GOD doesn't insist when we marry we have kids but he does bless many with that choice. When you do have them GOD says provide for them as well. But there was one scripture where GOD did order a man to impregnate a woman and he did not do it.
I believe it is a husband and wife's choice that GOD gives all married persons to have children or not. But if HIS plan calls for Mr & Mrs Smith to have a child when they have decided not to he will place it on their hearts to have a child. Now here is where sin enters. If the then after that they do not try then yes it is sin.
Of course, it is their choice. The question is: Is it a good choice. A sin is not merely an affront to kid, it is, humanly speaking, a misstep. Misstep on the stairs and you may break your neck. If enough people break their necks, then the hospitals will be full. If enough people make wrong choices about parenting, then society suffers. If enough choose not to have children, then society may cease to exist.