Nothing in the Bible identifies anyone, except Jesus, as a son or daughter of Joseph -- to say nothing of identifying them as a son or daughter of Mary. You're injecting a manmade tradition -- one that all of the "Reformers" rejected, BTW.
It's a sin in Judaism to exempt someone else from obeying mitzvot. One of the chief mitzvot is "Honor thy father and thy mother". For Jesus, on the cross, to give Mary to John (not a blood relative), means either that his alleged younger siblings were all dead, or that practically Jesus' last act in his life was to commit a sin.
BTW we know that at least some of the "brothers of Jesus" did not die before Jesus, because they're mentioned in Acts and elsewhere. We also know the parentage of some of the so-called "brothers of Jesus". It's in the Bible! James and Joses were the "sons of Alphaeus". Jude Thaddeus ("Judas, not the Iscariot") was the son of James, the grandson of Alphaeus. Look it up!
Looks like Paul disagrees with you and your opinion.
You remember Paul don't you?