objection
Jesus and Lucifer
Objection
Saying Jesus and Lucifer are spirit brothers is a caricature.
What is true
LDS doctrine does not morally equate Jesus and Satan.
Why it is not enough
The precise point is the premortal-family framework. Christianity says the Son created all things, including angelic beings.
Key question: Is Lucifer a created being made by Christ, or a spirit son in the same premortal family framework?
Do not use it as a shock line
The claim should not be framed as though LDS doctrine treats Jesus and Satan as morally equivalent. It does not.
The serious issue is category. LDS sources place Jesus and Lucifer within a premortal family framework of spirit children, with Jesus uniquely chosen and Lucifer rebellious.
Creator and creature cannot share that category
John and Colossians say all created things were made through Christ and for Christ. Hebrews places the Son above the angelic category.
If Lucifer is a created being, then he is made through Christ. If Jesus is the uncreated Creator of all created things, He is not one spirit child in the same broad order.
References
These are the public sources behind the answer, with LDS doctrine cited from LDS material where possible.
John 1
BibleBibleRef
If all created things came through Christ, Christ is not inside the created order.
Premortality
Official LDSThe Church of Jesus Christ of Latter-day Saints
Official LDS source teaching premortal life as Heavenly Father's spirit children.
Jesus Christ, Our Chosen Leader and Savior
Official LDSThe Church of Jesus Christ of Latter-day Saints
LDS manual chapter presenting Jesus as chosen in the premortal council and contrasting His plan with Lucifer's.
Satan, Topics and Questions
Official LDSThe Church of Jesus Christ of Latter-day Saints
Official LDS source identifying Satan as a spirit son of God who rebelled.