The Criminal Procedure Law stipulates that the period of detention is 15 days, the expiration of which can be extended for 15 days, and if it is a gang, roving crimes with the approval of the extension of another 7 days, so the maximum period of time is not more than 37 days. 37 days, generally have to be reported to the Procuratorate for approval of the arrest, that is to say, arrest or not arrest is by the Procuratorate to approve. Because it is two different departments, so generally before the arrest are offset to 37 days to come, so you do not have to rush, public security if the procedure is illegal, to give you a statement.
Robbery in China is a major crime, even if your brother is underage, as long as the full 14 years of age, the same to be held criminally liable, and after being detained are generally turned into an arrest, the possibility of bail are not very large. Since the lawyer, be patient, litigation cases have a deadline, as long as not more than the deadline, the lawyer has no good way.