Going through Depression. Him normal?

Hi, My brother is in Final year B.tech. He is going through depression(I may call it that). He recently faced a breakup after 4 years of serious relationship. The girl however didn’t gave him breakup in one go instead it was a torture period of 3 months, with on and off. Meanwhile he did every possible thing to make the girl stay. He used to think about her 24*7 and due to which he is not able to get over that situation.He doesn’t sleep well, even if he sleep he has dreams in which he remember all the good memories with her. My brother is now not able to move on with his life, he feels like cutting off from friends. He avoid social contact. He speaks things like "i wont marry, my life has ended, i dont want to come out of this phase, how can she be happy while i am not, i feel like taking revenge, i wont be living here since i have so many memories with her, what will happen to my life". He doesnt eat much, he cries a lot. What should we as family do to make him normal ?