these are very serious charges and your brother must get an attorney. for the two charges together it is 41-54 months on the low end and life in prison on the high end do to the indeterminate sentencing range involved. if he has any prior felony convictions, even juvenile felony convictions, his offender score will go up and drive the low end of the range much higher. weapons add additional time.
i agree with one of the previous attorneys that it will likely show up as dismissed. a typical criminal history record will show OD in the judgement column. meaning the case is on some sort of deferment. when you are completed the record switches to DO for dismissed after a deferral. Go down to the courthouse of record and talk with the clerks about the status of your record to be sure.
without knowing all the details, you have to wait 2 years after the sentence is completed to vacate a misdemeanor assuming no previous vacations. with the fact this was your sister, it was likely charged as a crime of domestic violence. a domestic violence misdemeanor will require 5 years. take a look at the statute, RCW 9.96.060. subsequent criminal charges delay you further.
mail contains identity; financial information or identification and its alleged you had intent to commit a crime with this identity. obtain the criminal information and consult with your attorney.
yes, you can bail a juvenile with exceptions. first contact the detention center, they should be able to tell you what the bail will be. bail is set at booking. bail will be revisited at the initial appearance in front of a magistrate. bail is not available for someone serving a sentence. juveniles are usually only released to the parent or legal guardian.