Summary: Faith family - second birth into a family where the blood really is thicker than water.
23 Now before faith came, we were imprisoned and guarded under the law until faith would be revealed. 24 Therefore the law was our disciplinarian until Christ came, so that we might be justified by faith. 25 But now that faith has come, we are no longer subject to a disciplinarian, 26 for in Christ Jesus you are all children of God through faith. 27 As many of you as were baptized into Christ have clothed yourselves with Christ. 28 There is no longer Jew or Greek, there is no longer slave or free, there is no longer male and female; for all of you are one in Christ Jesus. 29 And if you belong to Christ, then you are Abraham's offspring, heirs according to the promise.
Scripture quotations are from the New Revised Standard Version Bible, copyright 1989, Division of Christian Education of the National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved. 
Family resemblances can be startling. Take a grandfather’s picture from long ago and put it side-by-side with his grandson! If you’re the grandfather, it can be a surprise!
Josie Firstbrook and her husband had adopted their son, Eric, from Korea. When he was 5, they were having lunch at a restaurant, and Eric made conversation with a boy at the next table. At one point the boy asked Eric, “Why don’t you look like your mom?” “Cause she’s a girl,” he replied. 
The similarities of family resemblance aren’t all physical. In the “faith family” we also have some pretty important commonalities which draw us together. Here are three of them:
#1. Our Parent
23 Now before faith came, we were imprisoned and guarded under the law until faith would be revealed. 24 Therefore the law was our disciplinarian until Christ came, so that we might be justified by faith. 25 But now that faith has come, we are no longer subject to a disciplinarian, 26 for in Christ Jesus you are all children of God through faith.
When you were born, you had a mother and father, who, through a physical process, brought you into this world. But the Bible shows us another birth process that leads to entrance into the faith family.
Of course, the “law”, of which Paul writes, is the first five books of the Bible. Contained in these are the 10 Commandments. Many people have tried to be right with God on the basis of keeping the commandments – being good! But Paul says, “That’s impossible – that was never the intention for the law, and it is what the law could never do.”
Beside that – there’s no way you can keep those commandments perfectly throughout your entire life! Have you never told even a little lie? Never stolen as much as a paper clip? Never coveted your neighbor’s new car? You just can’t do it!
But Paul says we become children of God through faith. We have a common parent in God when we trust that He loved us enough to die for us, and we place our faith in Him to forgive us and become our Heavenly Father. It is the second birth; the first by earthly parents, and the second a “faith-birth”.