You've not heard me say it demands a second, third, etc. It's true you've posted some verses but they did not aid your argument. In fact, it has hurt your argument.
I've agree firstborn doesn't mean a second, third, etc, to which you agreed if I'm not mistaken.
As noted before....if Luke had used monogenes (only, unique) to describe Mary's firstborn then you'd have an argument. But Luke did not use this word.
That he used protokos, meaning first, first born, leaves the door open for other children. Couple that with the passage in Matthew regarding Joseph keeping Mary a virgin until Jesus was born along with all of the other passages in the NT where it is clearly noted Jesus had brothers and sisters means one thing.....Joseph and Mary had relations and produced other children!
Don't you think Luke, being a doctor and having researched his writing like he did, would be able to distinguish the difference??
Was Paul lying in Galatians when he said he met James, the Lord's brother??
Instead of relying upon these accounts, on which we all agree these accounts happened, the catholic relies upon one of the infancy gospels which they did not even feel warranted to include in their canon at Trent when they had the chance!!
Like I said you are entitled to your opinion. I will pray that the Holy Spirit softens your heart.