Jesus himself said that he and God were one.... that should be enough evidence for you...
It depends how one interprets that. When a man and a woman are married, are they literally
one flesh? Not literally, but in a spiritual sense yes. Hence why fornication is a sin against the body, the temple of God. Paul tries to explain that here:
1 Corinthians 6
15Do you not know that your bodies are members of Christ? Shall I then take the members of Christ and unite them with a prostitute? Never!
16Or don’t you know that he who unites himself with a prostitute is one with her in body? For it is said, “The two will become one flesh.”
17But he who unites himself with the Lord is one with Him in spirit.
18Flee from sexual immorality. All other sins a person commits are outside the body,
but whoever sins sexually, sins against their own body. 19Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own;
To get the whole breadth of what Jesus is saying in a spiritual sense, more of His sayings should be taken into consideration. Jesus views abiding in Him, that is to believe in Him and walk in His ways, as being in Him in a spiritual sense. In that sense, we can be one with Jesus, who is one with God, but we ourselves are not Jesus or God, though can be united spiritually.
John 14
20On that day you will realize that I am in my Father, and you are in me, and I am in you.
I'll post this again to hopefully give you a better idea of how this the hierarchy of the Trinity works.
1 Corinthians 15
27For “God has put everything under His feet.” Now when it says that everything has been put under Him,
this clearly does not include the One who put everything under Him.
28And when all things have been subjected to Him, then
the Son Himself will be made subject to Him who put all things under Him, so that God may be all in all.