Just like the sentence "they had no relations until she had given birth" must mean they had relations immediately after the birth.
No ... they likely had relations within the same period of time after the birth ... that husbands and wives do after the birth of their children today.
The fact that we waited, having achieved a certain point in our pregnancies, until the actual births of our children, to resume relations ... does not mean that we had relations in the hospital.
If this is the case, we can agree. You assume that they carried on as a normal average everyday family. We assume differently. But the text itself does not testify one way or another.
SD
You're assuming also that there were other brothers and sisters and that is part of your argument against perpetual virginity. If so, why did Jesus defy Jewish law and give over the care of his mother to someone who was NOT his blood brother? Someone who had no legal right to his mother?