The Apostle Paul recommends it.
That said, I do think that scripture leans more toward Mary and Joseph having a regular marriage after the birth of Jesus. One can cite children, Jewish tradition, etc.
But what would others call her if she had children by more than one Father? I think that always was what was being avoided.
If Mary had children by another man, we would give her every benefit of doubt and say that she married again after Joseph died. Mary is THE blessed Mother of Jesus.
“The Apostle Paul recommends it. “
Paul does not recommend it to married couples. He tells them to have sex regularly, except for brief intervals devoted to prayer.
To have the special child by the Holy Spirit wouldn’t be to cheat on Joseph. The bible says so. Such cheating could only happen with people.