For it was fitting for Him, for whom are all things and by whom are all things, in bringing many sons to glory, to make the captain of their salvation perfect through sufferings. For both He who sanctifies and those who are being sanctified are all of one, for which reason He is not ashamed to call them brethren. (Hebrews 2:11)
But now they desire a better, that is, a heavenly country. Therefore God is not ashamed to be called their God, for He has prepared a city for them. (Hebrews 11:16)
God is not ashamed of those who belong to Him by faith. Even as messed up as we are, God is not ashamed to call us His people. And Jesus is not ashamed to claim us as His brothers and sisters. For we are being sanctified by Him. Notice the tense, “are being sanctified.” That indicates that this process of being sanctified, being transformed as God’s own people, is ongoing. We are a work in progress.
Paul tells us that “it is God who works in you both to will and to do for His good pleasure” (Philippians 2:12-13). In other words, God is not only enabling us to do what pleases Him, He is even creating in us the desire to do what pleases Him. God has no doubt about what the end result will be. As Paul said earlier in his letter to the Jesus believers at Philippi, “He who has begun a good work in you will complete it until the day of Jesus Christ” (Philippians 1:6). And God knows exactly what that end result will look like — it will look like Jesus. “For whom He foreknew, He also predestined to be conformed to the image of His Son, that He might be the firstborn among many brethren” (Romans 8:29).
God is currently in the business of shaping us into the image of the Lord Jesus Christ, so that we may forever be like Him. And God, who sees the end from the beginning, is happy with that, because He is happy with Jesus. Jesus is happy with that too, which is why He is not ashamed to be “the firstborn among many brethren” and to call us His brothers and sister.