20.Why is Christ not ashamed to call of us "brothers"?

Because He who makes us holy (sets us apart unto God), and we who are holy, are all of one Father.

We are the younger brothers of Christ. We are smaller, not as mature, but we are His brothers.

Then said Jesus unto them, Be not afraid: go tell my brethren that they go into Galilee, and there shall they see me (Matthew 28:10).

Jesus saith unto her, Touch me not; for I am not yet ascended to my Father: but go to my brethren, and say unto them, I ascend unto my Father, and your Father; and to my God, and your God (John 20:17).

For whom he did foreknow, he also did predestine to be changed into the image of his Son, that he might be the firstborn among many brethren (Romans 8:29).