Read what is says, not what you think it says.
You are projecting.
You also deleted the "firstborn" from the passage, and your Greek rendering of the improper genitive preposition 'έως' is wrong - it should be rendered "until". But I already went over this with you weeks ago and you didn't refute it then. Heck, your interpretation is even in conflict with the Douray-Rheims translation and the RSV (along with scores of Protestant English translations).
I did not "delete" anything. Jesus is called "firstborn" because that what He is. When a son is born in a family, that son is firstborn. He is a firstborn even before there is a secondborn. "Firstborn" is a legal status that accrues to the first born son the moment that son is born, not at the moment a second one is born. So therefore "firstborn" is not an evidence of Christ having siblings. If I did not comment on it to you already, here it is now. I surely have no intention to avoid argument.
your Greek rendering of the improper genitive preposition 'έως' is wrong
I am sorry. Is this a typo? 'έως' is alredy in Greek. It is used in Matthew 1:24:
και ουκ εγινωσκεν αυτην εως ου ετεκεν τον υιον αυτης τον πρωτοτοκον και εκαλεσεν το ονομα αυτου ιησουν
, and it is used in Matthew 27:8:
διο εκληθη ο αγρος εκεινος αγρος αιματος εως της σημερον
"εως", of course, is used many other times, but I chose Matthew 27:8 because it is from the same human author and uses the word in the same way as in Matthew 1:25, to indicate that something that was the case prior to the moment it grammatically controls (ου ετεκεν τον υιον and της σημερον) continued even after that moment. Surely St.MAtthew did not mean to imply that the moment the ink is dry on Chapter 27, the field is renamed.
How you translate that in English is not something I ever argued about. The Evangelists did not write in English.