I have been wondering when you would enter the discussion, you always have interesting things to say.
This is an interesting problem for Mormons. How could the most evil person in the universe possibly be the brother of the God of the OT.
You must realize that you are looking at this relationship only since the earth was populated. You are not looking at it from the beginning. Therefore it is mind-boggingly impossible to reach the Mormon conclusion.
However, if you knew what satan/Lucifer was in the pre-mortal life, you might start taking another look. Lucifer (who on earth is satan) was an important spirit. Scholars tell us that the name Lucifer has reference to "light bearer". I believe he was a very powerful, and influencial spirit that was very close to God and Jesus. A Christian website at
Preparing For Eternity - Online Books, Bible Articles, Inspiring Stories, Bible Study Tools... has an online book called the Story of Redemption. In the first chapter it talks about Lucifer before his fall, and it says, Lucifer in heaven before his fall was next in honor to God's dear son.
So all I am saying is, if you look at Lucifer and Jesus in the pre-mortal life and before Lucifer's fall, they possibly sat next to each other and both were very powerful, honorable and influencial.
Isaiah is in fact is shocked that Lucifer fell, when he said in Isaiah 14:12, How art thou fallen, from heaven, O Lucifer, son of the morning? This fall was shocking for all of heaven because Lucifer was such a stalwart "light bearer" for God.
Of course the fall did take place, he did not go softly, he caused a war in heaven and he and 1/3 of the angels in heaven were thrust out onto the earth (see Revelations 12). It just went downhill fast from there. But if you could see him sitting next to Jesus, when he was following God, you would have a smaller objection that they were brothers.
Lucifer began to think of himself as higher than even his Father God. There is no doubt God created him. He used his free will finally against God and suffered the consequenses of his actions. Jesus on the other hand used his free will to follow the Father and his will. He said thy will be done. He went on to be the God of the OT and the Savior of all mankind. His now arch-enemy, satan, is on earth and as Jesus preaches the truth, satan does everything in his power to thwart the work of salvation.
So keep following Jesus and you will not have to even encounter satan and you will be rewarded in the Kingdom of God.