7 years? Usually with regular contacts, love
would have vanished and stable friendship would have form and
crystalized. After a long period of time, normally, one side cannot
picture themselves having a relationship with the other. Sometimes,
it's because they are so used to them being as friends, others,
purely because of platonic purposes.
I have to say this: Your initial decision to become 'sibling'
relationship is a route you took to foster better relationship with
him subconsciously. Its like a stairs - when you walk finish level
2, you can't just remain there. You created your own dimension of
relationship through 'kor-mei' relationship and in your heart, you
wished to get closer to him. So you were around when he was down
and all that. But your plan backfired because you ended up
nowhere.
Now that you realise all this effort was in vain to get him, you
rather retreat beause you can't take the full blow to see him
getting intimate with other girls. This is physical evidence of my
point above because if you return back to the original objective of
having this 'sibling' relationship with him is for your emotional
control as you claim to do so - it has never serve its
purpose at all.
You should have already woke up and prick your bubble dreams many
years back. Your hope is constantly fed by your subconscious
desire, even though the result has already been set. This is a
classic case of people following their heart and dull their mind -
so now, have you gain anything? Reject possible suitors? Pro-long
unneccessary emotional hurts? 
P.S: Stop this. Its time to leave your self-conjured shelter just
to make sure he is well everyday and learn to plan your own route
now. Don't even have to end this friendship because friendship are
priceless - end your overwhelming hope and desire. Stop catering to
his wants and needs and carve out a fresh life. Explore other
options and alternative.
Cheers
