The big problem your having is that you are looking at all of this from a strickly human point of view and not from God's view. God created mankind and told him to be fruitful and multiply. You as with all humans are the product of your parents and you have the same nature as your parents which is a human nature. Lions produce other lion cubs, birds produce birds and dogs begat dog puppies.
So tell me, who is the Father of Jesus Christ? In the case of Jesus Christ He is the only one that has two natures, one on His mothers side which is human and one on His Fathers side which is deity. Did you ever wonder why Jesus refered to Himself numerous times as the "Son of Man" and as the "Son of God?" The birth of Jesus Christ was a miracle where the Holy Spirit of God overshadowed Mary to give birth to a Son who is Jesus Christ. Read the account at Matthew 1:19-23. This is also why at Matthew 1:23 His name will be "Immanuel, which translated means "God with us."
This is also why John 3:16 says that Jesus Christ is the "ONLY" begotten Son of God as in there are no others. You can prove me wrong in all of this by simply giving me an example of a son that does not share the same nature as its father. You can't because it's a universal law. You also brought up the issue of "firstborn." The Greek word for firstborn is "protokos" and has a variety of meanings depending on the context.
Yes, it can mean firstborn by literal birth. It can also mean firstborn in the sense of "preeminence." Just read Romans 8:29. At Colossians 1:18 it says that Jesus Christ is the "firstborn" from the dead. Of course this not mean literal birth but He was the first one to resurrect from the dead in a "permanent" way defeating death so that we can have eternal life. So, please tell me what I have said that you consider "blasphemy?"
IN GOD THE SON,
bluto