My boyfriends 15yr old brother is really depressed, i think he may be ill. What !

My boyfriends 15yr old brother is really depressed, i think he may be ill. What can i do?

My boyfriend and best friend is 18 and i am seventeen, he has 4 brothers, who he is all very close with. One of them, is 15, he is a footballer and has been playing his whole life and is really good and commited, its basically his life, he got into this championship, two months ago, he was running and ripped his tendon, now hes learnt that he wont play for eightenn-months, and even then will never play well again.
To add to matters, one of his best friends, she and him dated & broke up now, have had a massive fight and have not been talking for weeks and he is realy upset.
He is wagging lessons at school, and not eating and falling out with his friends, i think maybe he is taking drugs. Nothing seems to help him, what can i do?
I am close with him as i have known them my whole life and i have asked him about it but he says nothings wrong. I can see cuttig marks on his wrists, this game has been his whole life.
How can i help him? I'm scared something really bad will happen?

2 weeks ago
The reason his parents dont know of this is because we go to a boarding school in England and they live in Spain and haven't seen him since after the accident, otherwise they would definitely notice, as they are very close to him. My boyfriends tried talking to him, but he can't seem to get through and he just wont listen.

If he has resorted to cutting, he is a danger to himself, and possibly to others. His parents need to be notified so they can go and get him. He needs professional help ASAP.