What is the significance of “firstborn among many brothers”?
Undoubtedly, firstborn carries with it the sense of preeminence. And much Scripture can be marshaled to the task of showing the preeminence of Christ; over creation, over the angelic world, over rebellious sinners, over the nations, over his beloved nation of Israel, and over his body the church.
What is striking in this context is that the one who benefits from believers being conformed to Christ’s likeness, is Christ. The result is that Christ will be preeminent in a new way. He will be Big Brother. It is as if God’s plan included bringing great joy to Jesus Christ in that Christ would experience the joy of having lots of younger siblings who shared the family likeness. The eternal fraternity is being formed. It is not just physical likeness that forms the family bonds, it is the common experiences and character traits siblings share. Imagine the laughter in heaven as we share our amazingly common experiences; a huge family of siblings who have suffered for one another, following the undefeatable example of our Preeminent Brother.