Is Jesus our brother?
No.
Jesus is the ONLY begotten Son of God.
No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father,
He hath declared Him. John 1:18
This is from Strong’s Exhaustive Concordance.
The Greek meaning of this portion of John 1:18 is as follows:

I hate the doctrine of John Calvin.
It twists the truth and it is difficult to explain to those who are caught in it how it is false
because it contains elements of truth.
I visited a church once which sang several songs about Jesus being our brother.
Their songs did not ring with the truth that Jesus was the Only Son of God,
that He was God in the flesh, that He has been given a name and a place above all other names.
Jesus is not our brother.
It is not like God the Father has all these little children
and Jesus is one of them and we are Jesus’ brothers and sisters.
Jesus is God’s One and Only Son and He is begotten of the Father.
Jesus was not created. He is one substance with the Father.
For by Him were all things created, that are in heaven, and that are in earth, visible and invisible,
whether they be thrones, or dominions, or principalities, or powers: all things were created by Him,
and for Him: And He is before all things, and by Him all things consist.
And He is the head of the body, the church: who is the beginning, the firstborn from the dead;
that in all things He might have the preeminence.
For it pleased the Father that in Him should all fulness dwell;
And, having made peace through the blood of His cross, by Him to reconcile all things unto Himself;
by Him, I say, whether they be things in earth, or things in heaven. Colossians 1:16-20
Galatians 4:6 explains it. We are His sons. We have been adopted.
And because ye are sons, God hath sent forth the Spirit of His Son into your hearts, crying, Abba, Father.
We are given the Spirit of Christ, who is One with God who sent His Spirit into our hearts
that we may call on God the Father as our Father.
it is not the same as saying Jesus is our brother and we are siblings, God’s sons and daughters.
He is begotten, we are created beings.
He has accepted us and we are given a place in His kingdom, in His family.
We remain created beings.
Jesus is God and God is Jesus. There is no separating them. I and the Father are One. John 10:30
He remains Christ, the Son of God and He gives us the ability to be joined with God the Father
as He is joined with God the Father as He is God. Jesus is Lord. He came to reconcile us to the Father.
While this should be elementary, some teachers teach that as children of God,
we are siblings with Jesus.
Jesus was always here. He was not a created being.
Jesus Christ the same yesterday, and to day, and for ever. Hebrews 13:8
For God so loved the world, that He gave His only begotten Son,
that whosoever believeth in Him should not perish, but have everlasting life. John 3:16
We are not at the same level with Jesus because we are children of God.
That is an honorary term. God does love us and has adopted us.
That they all may be one; as Thou, Father, art in Me, and I in thee, that they also may be one in us:
that the world may believe that Thou hast sent Me. John 17:21
As always, we must remain humble and in the fear of God as He bestows His pleasure toward us.
We do not become equal with Jesus, ever. He remains Lord of Heaven and Earth.