My parents doesn't let me grow a beard

Brothers, what should I do? My parents always trim off my beard very small in like every 20 days and I can't even grow a mid-sized beard. They say beard is sunnah, you don't have to grow it but I heard it's obligatory, right? If so then how can I deal with it? Not that they are abusive but just whenever they cut my hair, they also choose my beard and I am tired if convincing them to not to target my beard, what shall I do?