The chief priests were all related, and the high priest was chosen from them. The high priesthood rotated among them, kind of the way chairmanships on board tend to rotate among a few people. In Acts 4 Annas is back in power again and Caiaphas is mentioned second. The point is that this family killed Jesus. A family killed Jesus.
Families tend to stick together.
When they stick together with Jesus it is wonderful. We have families in this church which are a great blessing to the kingdom because they are committed to Jesus Christ. Generation after generation come to know Jesus as Savior and serve him. But it can work the other way too. If a family does not believe in Christ, it is very difficult for a member of that family to take a stand for Jesus.