>> Children are definately a blessing from God but I would not go so far as to say that childlessness is a sin.
I think you state it best. GENERALLY, self-imposed, purposeful childlessness is a willful blockade against the blessing of God that is a child. GENERALLY. BUT, that having been stated, to go all the way and make it an "eleventh commandment" that married couples must never avoid the possibility of having a child...now you've gone over into legalism; a sin in and of itself.
Plainly, scripture speaks to all mankind to "be fruitful and multiply". Plainly, also, scripture notes that "children are a blessing from God". These are both true statements, but they do not construct a mandate for the married couple UNLESS God gives the couple the conviction that it is a mandate for them.
So, while I could say, "Yes, God has convicted us that it would be sin for I and my wife to purposefully avoid having children", I cannot, on that basis, transform the conviction we have into a universally applicable scriptural mandate and try to impose it on others. It just isn't there.
This whole discussion is illustrative of the mechanism by which so many foolish arguments and schisms have arisen in the ranks of Christians; individuals having been convicted of God to do a certain thing according to a certain scripture illegitimately trying to impose that conviction on everyone else.
Simply put, any attempt to transform a legitimate, God-given personal conviction into a universally applicable spiritual law will result in conflict and dissention, and ought rightly be regarded as sinful. God convicted YOU about x-y-z, not everyone. If God wants everyone to have that same conviction, let Him do the convicting; you stay out of it and mind your own business and stick to the non-negotiables of scripture.
The message of the gospel is already "a rock of offense" and "a stone that causes men to stumble", there's certainly no need to go and manufacture more offenses.
I believe some of the problem lies in the fact that many Christians unknowingly limit the power of God as it relates to each individual. It took me many years of living and an education to be humbled by the power of God. And yet, I continue to doubt that I, or any man, has scratched the surface of knowing the true power of God. A god who can create a universe and hold it together for as long as he has can surely affect each of our lives. He has the power to convict one without convicting the other.
And too, probably applicable to this discussion is Jesus' instruction for us to "Judge not, and ye shall not be judged: condemn not, and ye shall not be condemned: forgive, and ye shall be forgiven:" This is perhaps the most difficult of Christ's instructions to follow.
Muleteam1