Of the same womb.
What a beautiful definition for the word which Jesus used to describe all believers, "...you are all brothers." Nicodemus asked Jesus if he had to enter his mother's womb a second time in order to be born again. Jesus answered, "I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit. Flesh give birth to flesh, but the Spirit gives birth to spirit."
All believers are of the same womb of the Spirit. We share the same parent, God, our Father. We are all brothers.
The Full Rights of Sons, Chapter X: Brothers - "...you are all brothers."