Do I need to read this manga [For your Love] before I read this one [Form of Sympathy]

not necessarily

Not much related, yuri was only side characters in for your love famous and good looking guy just know in for your love yuri will fight his friend cuz he gets to know his sister getting married and form of sympathy starts with yuri attending his sister's wedding and found his teacher Jiri (uke) crying in wedding of his sister , jiri was also on for your love giving candies to yuri cuz he was excellent student in school. -- that's all u need to rest u can start from of sympathy without reading for your love. -- hope that helps

I haven't read For Your Love yet, but i did read Form of Sympathy
Imo, you don't need it

Thanks guysss