How do i mend my broken heart?

my exbf and i dated for a year and broke up 11 months ago.he blocked me on facebook 7 months ago and theres no way i can communicate with him.i know his sister's facebook ,though i never really knew her cuz she lives abroad.should i write to her on facebook and tell him how much i love his brother and how lonely ive become since he left me?ive been clinically depress since the day he dumped me.i wanted to get back with him but he doesnt love me anymore,now all i want is to become friends with him again cuz thats what he promised when we broke ,that we would become friends for the rest of our lives.