Jesus can be both the Son of God and God because God is a Trinity.
Also, when we think of God the Father, we cannot think of Him like a king whose son, though royalty, is not the king. Jesus is actually spoken of in the Bible as both a prince and King, both as the Son of God and as God.
“For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.” Isaiah 9:6
“And he hath on his vesture and on his thigh a name written, KING OF KINGS, AND LORD OF LORDS.” Revelation 19:16
The Lord Jesus Christ is both Prince and King. He is both Son of God and God. The verse that we quoted above from the prophet Isaiah even says that He is "...The mighty God, The everlasting Father..."
No wonder Jesus said,
“I and my Father are one.” John 10:30
“Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me. If ye had known me, ye should have known my Father also: and from henceforth ye know him, and have seen him. Philip saith unto him, Lord, show us the Father, and it sufficeth us. Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Show us the Father? Believest thou not that I am in the Father, and the Father in me? the words that I speak unto you I speak not of myself: but the Father that dwelleth in me, he doeth the works. Believe me that I am in the Father, and the Father in me: or else believe me for the very works’ sake.” John 14:6-11
Jesus Christ cannot be the Son of God and not be God. Jesus even said that those who had not seen Him, but believed He was God would be blessed.
“And after eight days again his disciples were within, and Thomas with them: then came Jesus, the doors being shut, and stood in the midst, and said, Peace be unto you. Then saith he to Thomas, Reach hither thy finger, and behold my hands; and reach hither thy hand, and thrust it into my side: and be not faithless, but believing. And Thomas answered and said unto him, My Lord and my God. Jesus saith unto him, Thomas, because thou hast seen me, thou hast believed: blessed are they that have not seen, and yet have believed.” John 20:26-29