Matthew tells us in his Gospel that Jesus had brothers and sisters and even names the brothers.
Matthew 13:54-56 Coming to his hometown, he began teaching the people in their synagogue, and they were amazed. "Where did this man get this wisdom and these miraculous powers?" they asked. "Isn't this the carpenter's son? Isn't his mother's name Mary, and aren't his brothers James, Joseph, Simon and Judas? Aren't all his sisters with us? Where then did this man get all these things?"
Why is it so important to Catholics to believe that Mary was always a virgin when Scripture teaches that she wasn't?
And why is it so important to Catholics to think and believe that Jesus was an only child?
Oooo....oooo...I know.
Because "church fathers" and "popes" have proclaimed it as dogma and the Catholic Church believes it alone has the power to decide doctrinal truths, unerringly, under the "leading of the Holy Spirit". Of course, if these doctrines are deemed by future Church leaders to be in error, they are only "growing" in their understanding of knowledge. If doctrine contradicts God's written word, well then, "tradition" is on the same level as scripture and scripture must then be "interpreted" in light of this - it doesn't really mean what it says.
It would be easier for a camel to go through the eye of a needle, than for some to accept their particular religion is NOT the only, or even, THE true church Jesus said he would establish and lead into all truth. Too many things can crumble after that admission, and they CANNOT go there.
“Why is it so important to Catholics to believe that Mary was always a virgin when Scripture teaches that she wasn’t?
And why is it so important to Catholics to think and believe that Jesus was an only child?”
Because Satan likes this setup. The Goddess and Child motif has been a central figure of pagan worship since Nimrod’s Babylon. In fact, the Babylon Mystery Religion had as it’s central figure of worship a Queen of Heaven with Child.
This same Queen of Heaven is still worshiped today, only its name has been changed to “Mary”. Everything else about how it is worshiped has remained identical.
There have been books written on research people have done into the origins of the Roman edifice. Very scholarly books that detail exactly how this Babylon religion has been preserved in its entirety through the Roman edifice.
As has been witnessed on even just this thread alone, it is the easiest thing in the world to lead people into blasphemy and idolatry by using this setup. Something to do with the nature of how people are fallen. Satan sure knows how to sucker folk good.