No, Jesus and Satan are not brothers. Jesus is God, and Satan is one of His creations. Not only are Jesus and Satan not brothers, they are as different as night is from day. Jesus is God incarnate—eternal, all-knowing, and all-powerful, while Satan is a fallen angel that was created by God for God’s purposes. The teaching that Jesus and Satan are “spirit brothers” is one of the many false teachings of the Mormons (Latter-Day Saints) and, to some degree, also the Jehovah’s Witnesses. Both of these groups are properly labeled as cults because they deny essential Christian doctrine. While they use Christian terms such as Jesus, God, and salvation, they have heretical views and teachings on the most basic and essential Christian doctrines. (Please note that most Mormons today will vehemently deny that they believe Jesus and Satan are brothers. However, this teaching was most definitely a belief of the early Mormons.)
The teaching that Jesus and Satan are “spirit brothers” is born out of the Mormons’ misunderstanding and distortion of Scripture as well as some of the extra-biblical teachings they consider to be authoritative. Simply put, there is no way you can read the Bible using any type of sound hermeneutical principles and come away with the idea that Jesus and Satan are “spiritual brothers.” The Scriptures are very clear that Jesus is fully God, not some type of lesser god as the Mormons and other cults believe. The Scriptures are also very clear that God is transcendent above His creation, which simply means that there is no comparison between Christ the Creator and Satan His creation.
Mormons believe that Jesus Christ was the first “spirit child” born to God the Heavenly Father with one of his many wives. Instead of acknowledging Jesus as the one true God, they believe He became God, just as they will one day become gods. According to Mormon doctrine, as the first of the “spirit children” of God, Jesus had preeminence over Satan or Lucifer, who was the second “son of God” and the “spirit brother” of Jesus. It is ironic that they will use Colossians 1:15 as one of their “proof texts,” because it says that “[Christ] is the image of the invisible God, the firstborn over all creation.” Yet they ignore verse 16, where we see that “By [Christ] all things were created that are in heaven and that are on earth. Visible and invisible, whether thrones or dominions or principalities or powers. ALL THINGS were created through Him and for Him.” All things—thrones, dominions, principalities, or powers—includes Satan and his demons.
In order to believe that Satan and Jesus are “spiritual brothers,” one must deny the clear teaching of Scripture. Scripture says that it was Jesus Christ who created all things and that, as the second Person of the triune Godhead, Christ is fully and uniquely God. Jesus claimed to be God in many passages of Scripture. In John 10:30 Jesus said, “I and the Father are one.” Jesus was not claiming to be another, lesser god. He was declaring that He was fully God. In John 1:1–5 it is clear that Jesus was not a created being and that He Himself created all things. “All things were made through Him, and without Him nothing was made that was made” (John 1:3). How much clearer can it get? “All things” means what it says, and it includes Satan, who as an angel was himself a created being just like the other angels and demons are. Scripture reveals Satan to be a fallen angel who rebelled against God and Jesus to be God. The only relationship that exists between Satan and Jesus is that of creation and Creator; of the sinful created being, Satan, and the righteous Judge, Jesus Christ.
Like the Mormons, the Jehovah’s Witnesses also teach that Jesus and Satan are spiritual brothers. While some Mormons and Jehovah’s Witnesses might sometimes try to sidestep this teaching because it is so antithetical to what the Bible actually says, it is nevertheless what these organizations believe and is part of their official doctrine.
Mormons believe that, not only were Jesus and Lucifer “spirit children of Elohim,” but that humans are spiritual children, as well. In other words, they believe that “God, angels, and men are all of the same species, one race, one great family.” This is why they believe that they themselves will one day become as much of a god as Jesus or even God the Father. Rather than seeing the clear distinction in Scripture between God and His creation, they believe that one day they will be gods themselves. Of course, this is the same old lie Satan has been telling us since the Garden of Eden (Genesis 3:15). Apparently, the desire to usurp the throne of God is endemic in the hearts of men.
In Matthew 16:15 Jesus asked the important question: “But who do you say that I am?” This is a question that is essential to salvation and one that the Mormons and Jehovah’s Witnesses get wrong. Their answer that Jesus is the spirit brother of Satan is the wrong one. Jesus is God the Son, and in Him the fullness of the Godhead dwelt bodily (Colossians 2:9). He created Satan, and one day He will cast Satan into the lake of fire as the just punishment for his rebellion against God. Sadly, on that Day of Judgment those who fall for Satan’s lies will also be cast into the lake of fire with Satan and His demons. The god of the Mormons and Jehovah’s Witnesses is not the God who revealed Himself in Scripture. Unless these groups repent and come to understand and worship the one true God, they have no hope of salvation.