One place is: “Is this not the carpenter, the Son of Mary, and the brother of James, Joses, Judas, and Simon? And are not his sisters here with us?’ And they were offended at Him” (Mark 6:3).
Christ is the son of Mary, that is what it isaying, James and Joses are identified as the sons of another Mary. All the text is saying is that Jesus is the Son of Mary, none of the others are referred to as her children. James and Joses Mother is the “Other Mary” that is at the resurrection per MT, MK and Luke and is identified as the wife of Clopas by John in verse 25 of Chapter 19.
Again, no text ever identifies James, Joses, Judas, SImon or Salome as the children of Mary the Mother of Christ.
No orthodox theologian on the early Church interpreted those texts the way you are interpreting them. For a quick reference take a look at Saint Jerome’s Against Helvidius, he cites almost every orthodox Theologian going back to basically 100AD who reject your view.