The Koine Greek word "ἀδελφός" (adelphos;brother) is the singular form of its plural form "ἀδελφοί" (adelphoi;brothers), both of which are used in Matt. 13:55/Mk.6:3: "Is this not the carpenter’s son? Is His mother not called Mary, and His brothers, James, Joseph, Simon, and Judas?" (Matt. 13:55); "Is this not the carpenter, the son of Mary and brother of James, Joses, Judas, and Simon?"
The context in Matt. 13:55/Mk.6:3 show its definition "kinsman, or relative" applies in these verses, and one's kinsman/relative could be a sibling, cousin, nephew, or uncle, etc., but information needed to determine the type of family members is lacking in those same verses. You assert Jesus's four brothers (kinsmen/relatives) were His siblings, but you haven't provided evidence to support that.
I, however, provided evidence in the opening post showing (i) that James and Judas of the four were apostles James and Judas (Jude/Thaddeus) of Alphaeus (Matt. 10:3, Mk. 3:18, Lk. 6:15-16, Ac. 1:13), (ii) that this Alphaeus was the brother of Jesus's mother's spouse, and thus the four were Jesus's cousins, and (iii) that this James is the same person as "James the Less" (Mk. 15:40), "James the brother of the Lord" (Gal. 1:19), "James the Just," "James the bishop of Jerusalem" (Ac. 15:13-21), and "James the author of the Epistle of James" (Jas. 1).
Dude— it doesn’t matter how many times you say the same thing. You haven’t in the least precluded Jesus from having an actual brother named James. Same goes for Joses. That name means Joe Jr. You get that right?
It’s not a stretch to think he also had a brother named Simon— because scripture says he did! This would add context to him giving another Simon, who was not his brother (Simon bar Jonah) a nickname— Peter, to easily distinguish the two when talking about them. He does the same thing with John— nicknaming him Mark to distinguish from John the Baptist (John bar Zechariah) and John bar Zebedee.