It stands for you son of a b*txh, it can be used in a friendly way on friends when they are being an irritation and you are in enviroment of families and kids.
sahil called sid ysob because he met ismail without him.
It stands for YOU SON OF A BITCH (YSOB). It can be used to friendly call your friends ysob keeping it safe for the environment and families arround.
Sahil called sid YSOB because he met ismail.
I got you this ysob hat it means your sisters other bestie