There is no evidence in Scripture that Mary had other children. It is only by assumption that one can make that claim because no one other than Jesus is named as a child of Mary. Also, no one in Scripture is named as a child of Joseph much less as one of both.
I do understand why some hold the position that Mary and Joseph had children but that is not solidly supported in Scripture.
In considering both positions, I believe the early church writers and subsequent theologians who taught that Mary remained a virgin and had no other children.
With no Scripture to support the opposite belief, there is no question in my mind that the latter position is incorrect and was mainly developed out of anti Catholicism rather than real exegesis.
That's crazy...There is tons of scripture to support the idea of Mary having a brood of kids which has been posted countless times...There is zero support for Mary being sinless and celibate...