Of the 100 times that the word "firstborn" is used in the Bible most of the mentions have to do with the first birth of someone or some other living thing. The New Testament uses the term mostly in regard to Jesus being the firstborn of Mary. But in Romans, we are introduced to a new concept. The word firstborn is the term applied to the meaning of "prototype". However in the following verses we find that Christ is far more than a prototype of the human construct. Colossians says that Jesus, the image of the invisible God, is the firstborn of every creature.
This cannot refer to Christ being the prototype of every living creature, except in the commonality of all living creatures having life itself. Jesus tells us in John 14:6 that he is life. We all know that God gives eternal life unto any and all who receive His only begotten son. John tells us in his first epistle, chapter 5, that we have life if we have the son of God and if we do not have the son, then we do not have life. These verses make us realize that physical life is simply a breathing existence. While there, I must agree that physical life is generated and enabled only through Jesus Christ. "….by Him all things consist." Col. 1:17
The passage in Romans 8:29 tells us that God has predestined us (believers) to be conformed to the image of the son, (as He is the image of the Father.) That Christ might be the firstborn among many brethren. We have no inkling of what that really means, but the gist of it is that there are some great things in store for us who have put our faith and trust in the saviour.
In order to have the eternal life that God speaks of in the New Testament, one must be born again. We all know that the word that Niccodemus received that evening was not just a conversational explanation, but was a veritable law of God. Mankind does not get eternal life by anything he does or says. Eternal life is instantly generated in a person who hears the Gospel, believes the Gospel in his heart and confesses the Lord Jesus Christ. This salvation is not gained only by a mantra or quoting of "the sinner's prayer." Romans 10:13 is not a one time call. It is a continual communication with God, initiated and empowered by the Holy Spirit. Romans 8:26
Now, back to the subject of the firstborn. Normally we are satisfied with the doctrine of the Trinity. We readily admit that we cannot explain the Trinity. We are convinced and convicted that there are indeed three persons in the Godhead. God, the Father, God, the Son, and God, the Holy Spirit. We know that when Jesus was on earth, He prayed to His Heavenly Father and He taught us what the Holy Spirit does, acknowledging His concurrent existence. We know that while Jesus is in Heaven seated on the right hand of the Father, the Holy Spirit is here on earth, working through believers in His work of convicting men of sin, righteousness and judgment. When Jesus returns for us He will change our mortal bodies into a body like unto His own. We who are seated in heavenly places in Christ (Ephesians 2:6), will know as we are known and be partakers of His divine nature.
It is very obvious and can be proven that Jesus has plans for His own that far supersedes our fondest and fantastic dreams of what eternity really is. If and since He is the firstborn among many brethren, then it stands to reason that our future existence will be more that playing a harp on the edge of a cloud. I can hardly wait to get on board that Heavenly train.