This was a contentious issue at the time of the early Church. The question was whether Jesus was of the same substance as the Father, whether He was consubstantiate with God, or whether He was a creature like others. There were two opposing views: that of Arius who maintained that Jesus was a creature, albeit the first, and that of the other Church fathers led by Bishop Athanasius who said that the Logos represented in Jesus was consubstantiate with God.
This issue proved difficult because the earthly concept of ‘son’ had been applied in this case where Divinity was concerned and where obviously the human earthly concepts would not suffice. Divinity goes beyond the earthly and the spiritual and as a result we would have to change our ways of understanding such issues.
As far as God is concerned, the concept of ‘Son’ refers to a ‘part’ of. A Part of God necessarily has to be of the same substance as God. He has the ability to sever a small part of Himself to represent Him in Creation and this severed part nevertheless remains connected with Him. This part is what has become known as ‘Son’, Son of God. Jesus therefore is consubstantiate with God since He is a Part of God.