Not according to the Word of God…
If Jesus had had blood siblings, Under Jewish custom of the day, they would have been responsible for the care of His mother, yet, in spite of the case you would make, He went out of His way to see to her care by giving her to St. John as one of his last acts from the cross.
Also, it was virtually criminal for a younger sibling to mock or rebuke the first born son, and yet the word of God shows that this happened to Our Lord.
With historical documents that suggest that Joseph was a much older man and a widower with children, your assertions fails.
'Brethren of the Lord’
Mary: Ever Virgin (Fathers)
Even all three of the “pillars of the reformation” wrote in support of it.
My thanks to San Juan Catholic Seminars for publishing this in their Beginning Apologetics # 5 booklet.
The Perpetual Virginity of Mary:**
Martin Luther: “ It is an article of faith that Mary is Mother of the Lord and still a virgin… Christ, we believe, came forth from a womb left perfectly intact.” ( Works of Luther, Vol. 11, pages 319-320; Vol. 6, page 510.)
John Calvin: “ There have been certain folk who have wished to suggest from this passage [Matthew 1:25] that the Virgin Mary had other children than the Son of God, and that Joseph had then dwelt with her later; but what folly this is! For the gospel writer did not wish to record what happened afterwards; he simply wished to make clear Joseph’s obedience and to show that Joseph had been well and truly assured that it was God who had sent His angel to Mary. He had therefore never dwelt with her nor had he shared her company… And beside this Our Lord Jesus Christ is called the first-born. This is not because there was a second or a third, but because the gospel writer is paying regard to the precedence. Scripture speaks thus of naming the first-born whether or no there was any question of the second.” (Sermon on Matthew 1:22-25. Published in 1562.)
Ulrich Zwingli: “I firmly believe that Mary, according to the words of the gospel, as a pure Virgin brought forth for us the Son of God and in childbirth and after childbirth forever remained a pure, intact Virgin.” ( Zwingli Opera, Vol. 1, page 424.)