Hiya
First of all, it is never nice to see a member of your own family "going off the rails" especially since it's your own brother. Establishing some form of communication is vital for recovery, however it should be executed whenever the time is right. By that I mean before/after a family dinner, after a family visit to a relative/friend's house or even last thing in the evening BUT it has to happen if this is the form of cure you want(I am not aware of the personal circumstances that have a role, however given what you have written I can build a semi-complete picture of the scenario in question in my mind) for your brother. You speak of the style your brother has adopted, which is "chav". This is not good, especially since he knowingly drinks alcohol at the age of 14, worst yet we know because he had been caught red handed as he had came home drunk, which shows he had totally neglected the fact that this will shame his mother and father. This is only emphasized further by the fact that your brother shows no remorse for his actions in his family's presence. Obviously the group your brother "hangs out" with are corrupted(perhaps in a deindividualization sense, as your brother shows a complete lack of respect for his family at this point in time, and I would therefore imagine that the others in the group operate using the same philosophy to shape their actions) as the alcohol is either stolen or had been bought by an older member of the group. A more positive, moral influence must be in place for your brother, however that should only come after the root of the problem has been understood and appealed to.
Alcohol is addictive, it poisons the brain thus exposing us to a whole range of emotions and actions ranging from happy, head in the clouds misbehavior to depression. Users can become dependent on alcoholic drinks and weaning one off alcoholic drinks requires will-power and a positive influence that can show there is fun, happiness and ambition away from the booze(and the events that take place while consuming or getting it).
To address the root of the cause, appeal to your brother's sense of nostalgia, look back on the fun times you have both had, like holidays, pets, days out etc... or offer to invite your brother to a social gathering you may be having with your own friends, thus allowing him to mingle with people who are not dependent on alcohol and getting a "kick" from actions that cause them to lose respect for their elders/relatives. If that works out to be no avail then psychological help may be the answer. It can be easy to pour drugs like Prozac down your brother's throat should all else fail, however more natural, social solutions should be attempted first, and even with Psychological/medicinal help, the root of the problem will still have to be addressed(the root is what is causing your brother to lose respect for his family as well as why he may appear to have no guilt)
Good luck