I am genuinely not sure if this is real or someone trolling, but I don't want to not reply just in case.
The first thing you have to address is if the behaviour is because of an illness adhd/autism etc, or if it is because of his life experiences. The fact that you say a 10 year old butted a 5 year old and busted his nose, but it wasn't that bad is quite alarming.
If that kind of behaviour isn't serious to you, then your children will have leaned that from you. Equally you or someone he spends time with swears a lot, this will have normalized swear words and he will use them especially in times of anger/frustration.
If there isn't a medical reason for his behaviour, then I would make sure there isn't any abuse he is hiding, otherwise he has learnt the it by being exposed to it.
You need to remove everything in his life that contains the violence he is being exposed to, including games, dvd's, friends, relatives etc and the same goes for swearing. Any time he is violent make sure he loses his favourite items for a considerable time and every time he plays nicely with his brothers, tell him he has been great and get him a little something.
However whilst that will be a start I really think you should get some help, we foster and see a lot but that is some of the worst behaviour I have heard of.
The more I think about it, the more it I think it may come from pure frustration, or even be a call for help. Is there any other adult that has access to your son 1 to 1?