Mary's Perpetual Virginity revisited: if Jesus was the "firstborn" of Mary, wouldn't that indicate that there's at least a second born?

“Love the Lord with all your heart, and with all your soul,

and with all your MIND”--Matt 22:37

Question:  Mary's Perpetual Virginity revisited: if Jesus was the "firstborn" of Mary, wouldn't that indicate that there's at least a second born?  And does it really matter that she had other children? 
Scripture proclaims:

He is the image of the invisible God,
the firstborn of all creation.
For in him were created all things in heaven and on earth,
the visible and the invisible,
whether thrones or dominions or principalities or powers;
all things were created through him and for him.
He is before all things,
and in him all things hold together.
He is the head of the body, the church.
He is the beginning, the firstborn from the dead,
that in all things he himself might be preeminent. Colossians 1

And the Gospel of Matthew, which we hear at Christmas Vigils, proclaims:
 

And he knew her not until she brought forth her firstborn son.

(note:  again, "until" in Biblical language does not indicate subsequent actions.  See 2 Sam 6:23, 1 Cor 15:25 and 1 Tim 4:13 for examples of "until" meaning only "up to a certain point".)

It would seem that the Bible does state that Jesus is the firstborn, thus there were second born children of Mary.  That is, Scripture attests to the fact that Mary was NOT ever-virgin and had other children. 

It does indeed seem reasonable to assume, if I introduce my child as "Here is my firstborn", that I have other children.  Otherwise, wouldn't I just say, "Here is my only child"?

The Catholic response:
"This is another case where our modern understanding of terms interferes with understanding what the Bible meant at the time it was written. In biblical times, the term firstborn had great importance. The firstborn was to be consecrated to the Lord (Ex. 13:2); the parents were to redeem every firstborn son (Ex. 34:20). They weren’t supposed to wait until they had a second child to redeem the firstborn, and so the first son born to a woman was called the firstborn regardless of whether or not she had other children later on.

OBJECTOR: I still don’t see why the Church requires Catholics to believe that Mary remained a virgin instead of allowing them to have their own opinions. Does it really matter if Mary had other children?

CATHOLIC: Actually, it does matter. Every doctrine about Mary tells us something about Christ or something about ourselves or the Church."  source

That is, the teaching on Mary, Ever-Virgin, tells us about the sovereign divinity and numinous quality of that which she carried in her womb--the Word of God made Flesh.  She did not carry just a holy teacher, a man who would be a great healer and miracle worker, but God Incarnate. 

Again, can you imagine the womb which held God Incarnate later carrying anything else? 

Also, Exodus 13:1-2 provides an example of the understanding the ancient Israelites had regarding the term firstborn: "The Lord said to Moses, ‘Consecrate to me all the firstborn; whatever is the first to open the womb among the people of Israel, both of man and beast, is mine.’"

The "firstborn" were not given the designation because there was a "second-born." They were called "firstborn" at birth. That is, Jesus being "firstborn" does not require that more siblings be born after him. The firstborn was "he who opened the womb."

For more in-depth study visit these websites:

Catholic Bible online

Catechism of the Catholic Church online

Mary Ever-Virgin article

Another article on this

"Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect" - 1 Peter 3:15