It does...Jesus had blood brothers and sisters...Mary had a whole herd of kids after Jesus...Biblically, that is...
Nothing in the Bible identifies anyone except Jesus as a biological child of Mary. Absolutely nothing, not a single verse, nothing.
It mentions that Jesus had "brothers and sisters," but never calls those brothers and sisters children of Mary, and in fact specifically identifies their parents in some cases.
Amazing, and sad, how you can make dogmatic assertions without the tinest trace of Scriptural evidence for it.