The family consisted of parents grandparents aunts uncles and cousins. Their close family relatives would be such
Except that when you make a comparison with “like” passages found in N.T. scripture, they do not interchange these ideas as you suggest. The context can decide how the word “brothers” and “sisters” was used here quite nicely. If you want to interject a cultural norm to the passage in question, go ahead, but it won’t be enough. Two things are said in Jesus rebuke that tell the story.
Number #1 A prophet is not without honor but in his own town and among his own kin= relatives, AND!!! in His OWN HOUSE. (=HOUSEHOLD.) This word HOUSE is the exact same Greek word used in Mt. 2:11 when the Shepherds went into Mary’s literal house, her personal home. It is also the same Greek word used when Jesus entered Matthews house and reclined at the table. The point is, there is no spin here on the distinction between the town, the relatives, and the literal house of Joseph and Mary.
It is not unreasonable to tie-in the context of the argument (Which was: How can this be the Messiah?) to the fact that the narrative not only acknowledges but goes beyond hometown citizens and relatives. His brothers and sisters were included to the mix, making a distinction rather than a general statement. And the brothers were specifically named in association with Joseph and Mary and their daughters.
#2 We see this distinction in His rebuke between the hometown itself, (it’s citizens) along with His relatives and actual members of His HOME who would not honor Him, suggesting that even his brothers and sisters were not believing in Him at this point in time.
Then there is this thing called “transcending truth” When the holy Spirit guided Matthew’s hand to write this verse in Greek, over two thousand years ago, He easily could have cleared up any preconceived confusion or misunderstanding by directly saying, “these were not Mary’s biological children!, they were cousins!” (by employing that specific Greek word) So that we can be comfortable reading the passage at face value to understand what the holy Spirit wanted us to know in our generation today through an English translation.
But that is what we have now. The Holy Spirit chose the exact Greek words for Matthew to record. You just refuse to believe what your own Greek scholars must tell you if they are honest to the text. The word brothers and His sisters was a deliberate rendering, and consistent with other "like’ passages found in the New Testament. There is no suggestion here of a cultural norm to be applied without evidence.