Mac Miller's brother -- the one in charge of handling his estate -- showed up at his parent's home as they grieved together and planned for Mac's funeral.
Miller McCormick carried boxes of beer Friday into the Pittsburgh home of his parents.
Mac chose Miller as his personal rep to handle his estate. Mac wrote his will back in 2013 when he was only 21 ... unusual for someone so young -- especially someone who didn't have a wife and kids -- to write a will.
The will gives no detail as to how much money Mac left or to whom it will go. Mac created a trust -- something lots of people do to avoid going through probate -- and the trust documents were not filed with the court.
Whatever assets Mac left that were not part of the trust will go into the trust, so the will is effectively a hollow document.
TMZ broke the story ... Mac died last week of an apparent drug overdose.