The other brother is really a Reptilian who sows negativity and discord in the family in order to feed off the bad energies?
I suppose it could be any number of things, depending on your character's state of mind, and the time period. Can you clarify?
Ooh -- that's kinda heavy for my liking. But possibly one of them was inexcusably cruel to another family member.
Maybe the younger brother was abused badly as a kid and the older brother did nothing to help, or participated to ensure it wouldn't be him.
The older broth had a dream, i.e. to be the first man to climb this mountain unaided, and the younger brother achieved it before him. Would generate a lot of resentment. Or the older brother "stole" the younger brother's fiancee and then married her.
This is a rather open-ended question, really. I mean, basically list any reason why any person would kill any other person then determine how much your brothers actually love each other (some don't). Scenes from a Memory by Dream Theatre is about (among other things) two brothers fighting over a girl, a hardly unique scenario. You've got hatred born of jealousy, injustice, vendetta, misunderstanding, there really are countless possibilities. Given that this is your only post and your name, I'm going to assume these brothers are in their teenage years and may or may not be supernatural in some way. Given that the usual angst usually isn't good enough for *special* kids, fighting over a girl/woman is probably the easiest reason to use. Unless one of them leaves the family and comes back after joining some evil cult. That'd do the trick.
One of the brothers were their parents favourite. The other was unfairly treated and got too little of their inheritance. However, he stands in line to inherit his brother.
Maybe the hated brother was the "favorite" child and the attention went to his head and turned him into a creep.
Maybe they were raised in a very fundamentalist religious family and one of them reveals that he's gay. In their community, that might bring great shame to the family and would therefore be intolerable.
I like Mallory's idea, and Minstrel's. To suggest something more obvious, maybe the motive is jealousy. This could come in the form of a "favorite child," as some people have suggested. Or maybe the brothers are competing over a woman, over a job (or a higher position in that business), inheritance, or something like that. Something happens and a chain reaction makes them more and more hostile to each other as they fight back and forth over issues x and y. If one of them is continually cruel to the other, that could be the cause of mutual hatred and aggression--but first you have to pinpoint why they're in that position in the first place. If they're competing for something concrete, on the other hand, that's the cause right there, you don't need to have any deep reasons. Sibling rivalry combined with real-world consequences can create real violence.
the brother who wants to kill the other brother has some problems with vices(drinking, pills just destructive things) despite all this he is not a bad person. Yet his brother's constant judgment is getting on his last nerve and making him want to kill him.
My brothers love each other in my book - however their sister tries to kill them and succeeds in killing their parents. Her reason? Jealousy mostly, she was abused by her grandfather in a nasty way which turned her mind. Her reason for hating her younger brother is simply her mother looked at him differently, her father admired him more than her. Find out in a second book the older two are as a result of an affair by their mother and are not their father's children. She has a twisted version of love towards her twin brother and has used that as her excuse for invading his mind, having his lover almost killed and killing her parents who abused him. She then tries to kill him because he rejects her efforts to, 'protect him.'
For any of the usual reasons, love, hate, jealousy, financial gain, insanity, the difference being that they are brothers will make is, I think (unless in a state of uncontrollable anger) The story line and build up to the murder would need to be more intense than normal.
Ignore my last post. Reading your original post I see you are not talking murder. Reasons; betrayal, abuse, lost out in a love triangle, low esteem character with high profile bro. jealousy.
One word: Cthulhu Seriously though, as I have a brother, the things that I resent the most (although not nearly enough to kill him or even hate him) are as follows, from greatest to least. -whatever he does reflects back on me; if he annoys somebody, everybody thinks that I'm the same. If he has an argument with a girl I like, then she'll dislike me forever. It's annoying. -Feeling like I'm being watched all the time; everything I do is subject to judgement by my brother, whether he does it consciously or not. It works the same in reverse. Maybe the character gets really sick of this and thinks that he can only be an individual if his brother is dead? -the "he did it so I can't" mentality. In other words, if he does something, like start to write a book, then I feel like I can't or we'll be even more similar. I've overcome this, because there is NO WAY I'm not going to write. Hopefully this is helpful.
