Why do my parents seem to favor my brother?

it just feels like they do favor him. Wheneverhe haz friends over they are so obnoxious and loud. I can hear them in my room (which is upstairz my bros friends in the basement). my friends are kinda loud and my brother always points that out and says other not nice stuff about them in front of my parents. they never do anything. but tonight i said somethin mean about his friends and my parents got all mad at me and grounded me. i dont get it.