We've gone into this time and again, but the ancient Tradition of the Church states that Joseph was an older widower with grown children from a previous marriage, who married Mary when she was a teenager, and was more of a guardian than as a conjugal partner.
There is no word for "step-brother" in Hebrew or in Aramaic. Ergo, the "brothers and sisters" spoken of in the Gospels can just as easily be interpreted as "step-brothers" and "step-sistes" as they can be interpreted as blood brothers and sisters.
Protestants, relying on Scripture alone, interpret these passages as being blood kin. Catholics, relying on all other ancient Christian sources in concert
with Scripture, interpret them as step-siblings or other close relation, but not as the children of Mary.
James, the Bishop of Jerusalem, is often cited as being one of Jesus' brothers, as in Mark 6:3 and Galatians 1:19. Hegesippus (c. 180 AD) and Eusebius (c. 300 AD) also mention James as "the Lord's brother", but Eusebius (who wrote a history of the Early Church based on primary sources no longer available to us), specifically identifies him as "the son of Joseph", and Hegesippus mentions that James was past the age of eighty when he was martyred in 62 AD. This would make James more than twenty years
older than Jesus, and as Luke plainly tells us, Jesus was Mary's "first-born son". Ergo, if Hegesippus is correct, then James had to be a step-brother, unless Joseph was building time machines in his carpenter's shop.
Catholics think Mary was a perpetual virgin. Protestants think she had more children. It's not a salvational issue either way, so frankly, what difference does it make? the only reason I can think of for even bringing it up is to attempt to discredit Catholic belief, by saying "If they're wrong on
this count, then they can be wrong on
others."
Fortunately, if one looks at the vast collection of early Christian writings from the first four centuries of the Church as a whole, there is more than enough evidence to indicate that Mary remained a virgin her entire life after giving birth to Jesus. The only way you can deny it is to discount some of the evidence because it isn't found in the Bible, and that's not a tactic that will stand up in court.
"I have evidetial proof here, Your Honor, in five different exhibits. However, because the results they indicate don't agree with the way I believe the case ought to turn out, I'd like to dismiss four of them."
I wonder what the judge would say?