How can Jesus be God if he is called the Son of God?

   The word "Son" is an expression of family relationship.  The phrase "Son of God" is expressing His absolute deity as the only begotten of the Father (Matthew 16:16).  Jesus was not the son as we look at it in an earthly sense.  He was born of a virgin and was immaculately conceived by the Holy Spirit.  God performed a miracle to present Himself in the flesh to be an atoning sacrifice for all of mankind.  Jesus is also called the "Son of David" (Matthew 9:27) which was an expression of His kingship!  He was also called the "Son of Man" which spoke of His humanity (Matthew 16:13). "A virgin shall conceive and bear a Son and shall call His name Immanuel..." (Isaiah 7:14).  Immanuel means - God with us!  Jesus was also called the Mighty God (Isaiah 9:6).