The devil’s brother you say. Even before the devil sinned, that could not have been true. Jesus may have come to be a brother to MEN, but the bible (e.g. Hebrews) appears to disavow that anyone (let alone God) can be a brother to ANGELS.
In Mormonism, Jesus, Lucifer and the rest of us all are equal.
Both Jesus and Lucifer wanted to be “Savior” but God chose Jesus because he would give us ‘free agency’. Lucifer got mad and thus didn’t get a body so he can’t earn his Godhood like Jesus did. To Mormons, Jesus is proof we can be Morally perfect in this life and earn Godhood like He did. Not biblical at all.
I can source all of this if you would like.