What aspects would be needed to make up a kingdom? First and most important you would need willing people/subjects/servants. If you don’t have subjects then you are NOT really a king. If they are not willing subjects then you are a tyrant. You would also need a region or kingdom (king’s domain). Finally a set of laws by which the kingdom is maintained.

We see Jesus states he has a kingdom, He has servants, and He has a set of laws by which he desirer his kingdom to be maintained. This shows that He is a king. Not the king of an earthly kingdom, as of yet, but a spiritual kingdom. 

Jesus answered, “My kingdom is not of this world. If my kingdom were of this world, my servants would have been fighting, that I might not be delivered over to the Jews. But my kingdom is not from the world.”

John 18:36 ESV

Nathanael, a newly added follower, was inspired by God to make a declaration of Jesus kingship. calling his “teacher, Son and king”. Nathanael was looking for the promised delivering king, but would soon believe in the spiritual kingdom.

Nathanael said to him, “How do you know me?” Jesus answered him, “Before Philip called you when you were under the fig tree, I saw you.” Nathanael answered him, “Rabbi, you are the Son of God! You are the King of Israel!”

John 1:48-49 ESV

Jesus talked various time in the gospels about the “Kingdom of God” or “Kingdom of Heaven”, these statements are interchangeable. When Jesus sent out His disciples He told them to tell the people that “The kingdom of heaven is at hand.” Matthew 10:7. This was not just a declaration, of Jesus kingship but also an invitation for people to enter into a new kingdom, as willing subjects.

We can see that the writer of the old testament was speaking of Jesus as the coming King. This is why many Jews did not believe in Jesus they were expecting a warring king, to deliver them from Roman tyranny, not a Servant King.

For to us, a child is born, to us, a son is given; and the government shall be upon his shoulder, and his name shall be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace. Of the increase of his government and of peace, there will be no end, on the throne of David and over his kingdom, to establish it and to uphold it with justice and with righteousness from this time forth and forevermore. The zeal of the Lord of hosts will do this.

Isaiah 9:6–7 ESV

I saw in the night visions, and behold, with the clouds of heaven there came one like a son of man, and he came to the Ancient of Days and was presented before him. And to him was given dominion and glory and a kingdom, that all peoples, nations, and languages should serve him; his dominion is an everlasting dominion, which shall not pass away, and his kingdom one that shall not be destroyed.

Daniel 7:13–14

Judas one of his disciples also believed that he was to be the one who would deliver the Jewish people for Roman, that he lead the Roman soldier to where Jesus was. I believe Judas believed that this would cause Jesus to arise and begin delivering the people. After the death, burial, and resurrection of Jesus, his follower continued to proclaim the Kingdom of God and the Lordship of Jesus.

I charge you in the presence of God, who gives life to all things, and of Christ Jesus, who in his testimony before Pontius Pilate made the good confession, to keep the commandment unstained and free from reproach until the appearing of our Lord Jesus Christ, which he will display at the proper time—he who is the blessed and only Sovereign, the King of kings and Lord of lords.

1 Timothy 6:13–15

After Jesus showed Himself after the resurrection Jesus ascended in to heaven and there he was seated at the right hand of God the Father. The right hand speaks of authority, that the Father gave authority to the Son.

. . . that he worked in Christ when he raised him from the dead and seated him at his right hand in the heavenly places, far above all rule and authority and power and dominion, and above every name that is named, not only in this age but also in the one to come.

Ephesians 1:20–21

He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power. After making purification for sins, he sat down at the right hand of the Majesty on high, having become as much superior to angels as the name he has inherited is more excellent than theirs.

Hebrews 1:3–4

The heavenly realm also declared in the kingship of Jesus, when Gabriel can to Mary he made reference to the unborn child would be given the throne of David, one of the Jewish people’s greatest kings.

And the angel said to her, “Do not be afraid, Mary, for you have found favor with God. And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. He will be great and will be called the Son of the Most High. And the Lord God will give to him the throne of his father David, and he will reign over the house of Jacob forever, and of his kingdom, there will be no end.”

Luke 1:30-33 ESV

Along with the heavenly host, there were many people in the gospels that called out to Jesus using the phrase “the Son of David”. These people were proclaiming that Jesus was a prince and rightful heir to the kingship.

We also see in the book of Revelation written by John for some time in the future (book of prophecy). This book speak of the time when Jesus will be coming back to the earth to set up His natural kingdom.

. . . and from Jesus Christ the faithful witness, the firstborn of the dead, and the ruler of kings on earth. To him who loves us and has freed us from our sins by his blood and made us a kingdom, priests to His God and Father, to him be glory and dominion forever and ever. Amen.

Revelation 1:5–6

They will make war on the Lamb, and the Lamb will conquer them, for he is Lord of lords and King of kings, and those with him are called and chosen and faithful.

Revelation 17:14

He is clothed in a robe dipped in blood, and the name by which he is called is The Word of God. . . . On his robe and on his thigh, he has a name written, King of kings and Lord of lords.

Revelation 19:13, 16