Mark chapter 6:3...just read it....one doesn't need to strain himself or ones intellect by trying to tease the term "cousin" from the words brother and sister...or Matthew 12:46 where it refers to Mary and the Brothers of Jesus "wishing to speak to him!
THESE SCRIPTURES WERE WRITTEN BY THE FIRST CHRISTIANS YOU SO POINTEDLY REFERRED TO!
Mary had other kids! Unless all of Catholicism is prepared to call scripture false...are you prepared to stand before Jesus and say to him he had no siblings in the familial sense?
Technically of course, Jesus was placed in Mary's womb by the Holy spirit so that there is no "direct" biological link to his brothers and sisters. Yet Momma was the model of a good Jewish wife and raised other children with Joseph...does this mean this diminishes her role as Jesus mother...heaven forbid! The Bible states..."The marriage bed is undefiled" There is no sin in married sexual life!
I understand the statement that Jesus was the firstborn. Even if you only have one child the first is still the first. This was important because of Jewish law.
However, on the cross when Jesus gave Mary to the keeping of John that would have been a gross violation of Jewish law because she would have "belonged" to her "other children". So you (general you) mean to say that Jesus obeyed the law except for that one little bitty thing?
You are reading the Bible that is interpreted from Aramaic to Greek to English. Unfortunately, there is no Aramaic word for "cousin", so the Greek renders the word - brother. Thus, the confusion.
Rather than making the claim that Catholics believe Scripture is false, I think I will go with the Catholic tradition of 2000 years and say your interpretation is incorrect.
Regards