Since the Millennium is for 1,000 years, those born towards the end of the Millennium would be rebellious, otherwise there would not be so many at the battle of Gog and Magog:Thanks bro Nehemiah again.
One more thing: Can you tell me if you believe those that are left of all the nations that went against Jerusalem were SAVED or UNSAVED people? I believe most likely saved, since saved people enter the millennium.
https://www.kingjamesbibleonline.org/Revelation-20-7/
And when the thousand years are expired, Satan shall be loosed out of his prison, And shall go out to deceive the nations which are in the four quarters of the earth, Gog and Magog, to gather them together to battle: the number of whom is as the sand of the sea.
(Rev 20:7,8)