What is the significance of Jesus calling his disciples 'my brethren'?

In John 20:17, when Jesus instructs Mary to tell his disciples that he is ascending to 'my Father and your Father, and to my God and your God,' he profounds the familial relationship he shares with his followers. The use of 'brethren' highlights the deep unity that believers have with Christ, designating them not merely as servants but as part of God's family. This signifies our status before God as adopted children, which is central to the doctrine of union with Christ. Believers are not only recipients of grace but share in the inheritance and relationship of sons and daughters of God. This intimate connection reassures Christians of their identity and security in Christ, reinforcing the essence of sovereign grace theology.