You cannot blame the police or the lawyer for this delay.
This is routine and such things are routine and common.
The police will not change their attitude or approach just because it is your brother involved in this.
If you do not cooperate with the police they file an application before high court seeking cancellation of bail on the grounds that the accused is no cooperating for investigation.
The high court may immediately cancel the bail on the basis of the arguments made by public prosecutor for non cooperation by the accused with the police.
Don't Create problems for yourself by such negligent attitude.
The police may take 90 to 180 days for completing the investigation and submit charge sheet before the trial court as a rule, hence you cannot seek expeditious investigation.