The “word of God in sacred tradition” as you call it, is a theological concept found outside the apostolic circle and was never taught as a truth at any time in the first two centuries of Christianity.
But your answer was a predictable dodge, my friend. He is called the “first born” son for a reason. (Mt. 1:25; Lu.2:7) Even the Apostle Paul recognized Christ’ brothers when he said, "Do we have no right to take along a believing wife, as do also the other apostles, the brothers of the Lord and Cephas? 1st. Cor. 9:5 You know the story of Mary, along with her 4 sons, approached Jesus with an interesting dialog, wanting to speak to Him. His response was directly pointed to the messenger
"… who is my mother and who are my brothers?.. And He stretched out His hand toward His DISCIPLES (making a distinction) and said, 'here are my mother and my brothers. Mt. 12:46
All of these passages are divinely placed within your reach if you can accept the word of God above your tradition.