The closest bond a person will ever have in their life is with their spouse or significant other. The next closest bond is between brothers.
“ A brother may not be a friend, but a friend will always be a brother. ”
— Benjamin Franklin
But what is a brother? The word is defined as follows:
1.a man or boy in relation to other sons and daughters of his parents.
2. a male associate or fellow member of an organization: fraternity brothers.
3. (also brothaor bruthah ) informal for a black man (slang)
4. a fellow human being.
5. a thing that resembles or is connected to another thing;
6. Christian Church a (male) fellow Christian.
7. a member of a religious order or congregation of men
8. used to express annoyance or surprise.
The main male characters were not related to each other by blood. Their only connection was living through a traumatic event on par with soldiers on a battle field.
The did not voluntarily join a club like fraternity brothers, who swear an allegiance to each other. There time together was marked by disputes, leadership struggles and fights.
The one thing that connected them together was the fact that they were on some immortal and potentially crazy man’s “list of candidates.” They had nothing in common, except a medical background of Jack and Bernard.
None of them had outspoken Christian values or grouped people in a congregation based upon those principles. In fact, most of the main male characters were generally annoyed by the personalities, traits and opinions of their fellow castaways.
So the only true connection between Jack, Sayid, Sawyer, and Locke were the survival of a plane crash and the mutual struggles on the island. Yes, they were fellow human beings but one contained a monster (Sayid's violent tendencies) and one became a monster (Locke).
Were Jack and Sayid close friends? No. They were colleagues who often agreed on strategy to survive. But Sayid was always looking to cover his own back first.
Were Jack and Sawyer close friends? No. They were rivals for materials on the island after the crash (medical supplies, weapons, food). They were rivals for Kate's affection. They never truly got along. Sawyer did not stay to help Jack fight MIB.
Were Jack and Locke friends? No. They never met eye to eye on their view point of science verus faith to explain the unnatural elements of the island. Locke was too trusting, and Jack was too stubborn in his personal views. They never truly got along.
Were Jack and Jin friends? No. They could not communicate because of a language barrier. Jin favored isolation away from Jack's main group. There was some respect for their skills, but Jin never fought for Jack's vision of the means to survive on the island.
So none of the major male relationships have any hard element of brotherhood, a strong bond through thick and thin, the best of time or the worst of times.
So the brotherhood angle of the LOST saga again falls on the realationship between Jacob and MIB. A relationship founded upon a kidnapping by a crazy woman, no father figure, parent constraints and child rebellion, and finally murder. Jacob and MIB's home was not the island but it was their living hell. Their crazy mother who killed their real mother raised them in secrecy of their true past. They lived in isolated place under rules that granted them a form of immortality under the pains of imprisonment.
One cannot say that Jacob and his brother were actual friends. They merely tolerated each other growing up as children. They did not have other humans to develop social skills or gain knowledge outside their adoptive mother's rules. When MIB broke away from his mother's dictatorship as a young adult to live with the survivors of the shipwreck, his one goal was to get away from the island. Jacob did the opposite. He stayed with Crazy Mother and broke the one family tie he had on the island.