Thanks for your question.
There are two approaches to answering this question and they support each other.
- Jesus spoke for his Father and spoke of the Kingdom as his Father's kingdom "Thy Kingdom come..." For example, when Solomon became king over Israel we are told that he sat on the "Throne of the LORD over Israel" [1 Chronicles 29:23]. He was indeed king of Israel but the REAL king was always God. In the same way Jesus called the Kingdom in which he will be king, "his Father's kingdom." [Matthew 26:29]. He also said that he came to do his Father's will. [John 4:34]. So everthing to do with his work on behalf of the world and his brothers and sisters proceeds from God. So God is always the primary King of the Kingdom. The example of Joseph as a type of Christ is instructive. The relationship of Joseph and Pharaoh is a foreshadowing of the relationship that would exist between Jesus and his Father.
- In 1 Corinthians 15:20-28, Paul tells us that there will come a time when, after the 1,000 years, Jesus turns the Kingdom over to God and steps down from his position of authority and God is all in all. That will be when the "Kingdom" really comes into its own. Then only God will be "in charge" and all mankind who have survived and been granted immortality will be "equal unto the angels."
I hope that was helpful,