You could very well be right. But since Mary and Joseph were in fact a married couple, it is safe to assume they did what other married couples do.
I don`t believe Jesus would have appointed John to care for Mary if she had other children and I doubt if the other children would have went for it any way.
This would be rare today in a God believing family, there would be a fight.
It shows in John 7 that the brothers of Jesus did not see him as any authority and in fact indicates they may have thought they should have a little authority over him.
They don`t sound like little brothers to me as I had several big brothers and it don`t work that way.
OK. I see your POV. Obviously we are talking about events that occurred over 2000 years ago, long before there was TV, radio, the modern day news media, internet, and other forms of modern communication. I simply assume that because Mary and Joseph were a married couple, they did the same things as other married couples do. Hard for me to imagine Joseph as a passive wallflower standing alone in a corner somewhere and sleeping in a separate bedroom. I get the impression it was a close and loving marriage. I have no problem believing the marriage was consummated after Jesus was born. I don’t know why others do.