I’ll go along with what the Bible states, which is that Mary had other children.
Chapter and verse?
It says that Jesus had “brothers” and “sisters”. The Bible does not say that Mary was the mother. In fact, some of those “brothers” are mentioned elsewhere as children of Mary Cleopas. The Bible does not say one way or the other about Mary having other children — a collective of cousins, second cousins, adopted children, etc. would commonly be referred to as “brothers” in antiquity.
If Mary had other children, the belief in her perpetual virginity would not have taken hold, as they would certainly be known to the early Christians. Yet, the Early Church referred to her systematically as “the Virgin”.