Several people in this forum have asked me to defend my position on Mary. So, I will try.
The Bible is silent on the issue of the perpetual viriginity of Mary. While there are references to "brothers" and "sisters" which on the surface seems to support the idea of Mary having other children, the fact is we know nothing about their exact relationship with Jesus. The Bible is silent on these family members untill Jesus is 30! It makes sense that if there were other childeren involved in the return from Egypt or on the trip from Jerusalem, there would be some mention. Now I realize that this is not strong evidence but it is circumstantial and must be acknowledged.
However, there is the additional problem, that even if Mary did not have additional children, that does not mean she remained a virgin. So we must look at the evidence we have. The Bible records that the Angel told Joseph to take Mary as his wife. But it also makes it clear that he had no relations with Mary while she was his betrothed, nor did he have any relations while she was pregnant. Here, we must ask, why? Nothing in Jewish law forbids a man having relations with his pregnant wife. But we see that Joseph choose not to.
An Explination for this may be found in other documents from antiquity. In the Protoevangelum of James written in the 2nd century we read the early Christian legend that Mary was a temple virgin under a life-long vow of celebacy. And that she was entrusted to Joseph to care for her. This is not unheard of in antiquity. And, it would explain why Joseph did not have relations with her while she was pregnant.
Add to this that in antiquity, in the early church, there is no counter argument. There is no one claiming Mary was not a virgin, no one claiming relatives of Christ. As a matter of Fact we know from other early christian sources that James "the brother of the Lord" was in fact a son of Joseph, a view supported by the Protoevangelum.
In short, after prayer and study, there appears to be no evidence from the Scriptures, antiquity or Tradition to support the idea that Mary did not have other children. At least, that is my opinion.