Jesus Christ is never referred to as ‘brother’ but the Bible speaks of him having ‘brethren’ both natural and spiritual as follows:
Matthew 12:46 While he yet talked to the people, behold, his mother and his brethren stood without, desiring to speak with him. 47 Then one said unto him, Behold, thy mother and thy brethren stand without, desiring to speak with thee. 48 But he answered and said unto him that told him, Who is my mother? and who are my brethren? 49 And he stretched forth his hand toward his disciples, and said, Behold my mother and my brethren! 50 For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother.
Matthew 13:55 Is not this the carpenter’s son? is not his mother called Mary? and his brethren, James, and Joses, and Simon, and Judas? 56 And his sisters, are they not all with us? Whence then hath this man all these things?
Matthew 23:8 But be not ye called Rabbi: for one is your Master, even Christ; and all ye are brethren.
Matthew 28:10 Then said Jesus unto them, Be not afraid: go tell my brethren that they go into Galilee, and there shall they see me.
Mark 3:31 There came then his brethren and his mother, and, standing without, sent unto him, calling him. 32 And the multitude sat about him, and they said unto him, Behold, thy mother and thy brethren without seek for thee. 33 And he answered them, saying, Who is my mother, or my brethren? 34 And he looked round about on them which sat about him, and said, Behold my mother and my brethren! 35 For whosoever shall do the will of God, the same is my brother, and my sister, and mother.
Mark 6:3 Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him.
Luke 8:19 Then came to him his mother and his brethren, and could not come at him for the press. 20 And it was told him by certain which said, Thy mother and thy brethren stand without, desiring to see thee. 21 And he answered and said unto them, My mother and my brethren are these which hear the word of God, and do it.
John 2:12 After this he went down to Capernaum, he, and his mother, and his brethren, and his disciples: and they continued there not many days.
John 7:2 Now the Jews’ feast of tabernacles was at hand. 3 His brethren therefore said unto him, Depart hence, and go into Judaea, that thy disciples also may see the works that thou doest. 4 For there is no man that doeth any thing in secret, and he himself seeketh to be known openly. If thou do these things, shew thyself to the world. 5 For neither did his brethren believe in him.
John 7:10 But when his brethren were gone up, then went he also up unto the feast, not openly, but as it were in secret.
John 20:17 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. 18 Mary Magdalene came and told the disciples that she had seen the Lord, and that he had spoken these things unto her.
Acts 1:14 These all continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren.
Acts 3:21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began. 22 For Moses truly said unto the fathers, A prophet shall the Lord your God raise up unto you of your brethren, like unto me; him shall ye hear in all things whatsoever he shall say unto you. 23 And it shall come to pass, that every soul, which will not hear that prophet, shall be destroyed from among the people.
Acts 7:37 This is that Moses, which said unto the children of Israel, A prophet shall the Lord your God raise up unto you of your brethren, like unto me; him shall ye hear.
Romans 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.
1 Corinthians 9:5 Have we not power to lead about a sister, a wife, as well as other apostles, and as the brethren of the Lord, and Cephas?
Galatians 1:19 But other of the apostles saw I none, save James the Lord’s brother.
Philippians 1:14 And many of the brethren in the Lord, waxing confident by my bonds, are much more bold to speak the word without fear.
Colossians 1:2 To the saints and faithful brethren in Christ which are at Colosse: Grace be unto you, and peace, from God our Father and the Lord Jesus Christ.
Hebrews 2:11 For both he that sanctifieth and they who are sanctified are all of one: for which cause he is not ashamed to call them brethren, 12 Saying, I will declare thy name unto my brethren, in the midst of the church will I sing praise unto thee.
Hebrews 2:17 Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people.
I hope you have found this helpful.