Tomtraveller,
Huge thanks for your support!
If you can then I would recommend you to post your message also in other forums like below. There are couple of travel forums except Lonely Planet to send you messages to more people. I have got 3 popular forums for your kind information:
http://www.tripadvisor.com/ShowForum-g293889-i9243-Nepal.html
http://www.trekinfo.com
http://www.yentra.com/
Hope that helps you and wish you all the best!
Even if you want then you can write me private message. If you need any help then I will do my best for your kind help!

Sima
Was your brother carrying lots of money (or cash). If he was, and people saw this (say when he was paying for something), it might have made him the target for theft - obviously this is just speculation.
Have you checked with the airlines whether he has flown out of Nepal - I do not know how you do this, but people in your government should be able to advise you on this.
If, as I strongly advise, you go to Nepal and you, or someone, starts checking lists of visas, TIMS cards, trekking permits, records at entry points to trekking areas and other places where trekkers and tourists have to sign in, do check the names on all lists VERY CAREFULLY. Quite often Nepali officials get first names and family names (surnames) mixed up. This has happened many times when I have been trekking - so anyone looking for me would have to look under both names - many officials, especially in the areas outside Kathmandu, have little education and struggle with English (which uses completely different letters/characters from Nepali). It would help to get your brother's passport number - this is often put on trekking and other lists - generally this is recorded correctly.
Please also note that Nepali officials do not always want to correct a name if they have written it incorrectly, as they do not want to "lose face".
Obviously try and generate as much publicity as possible. Please note that people travel to Nepal from many countries, and they may then travel on to other countries before returning to their own country, so the more publicity you can get, the better. He may well have decided to spend time in a monastery.
During my various visits to Nepal, I have heard of one or two tourists planning to cross illegally into Tibet, however stupid that idea may seem. Even though the main routes are presumably very well policed by the Chinese government, there may well be other routes through remote valleys etc that locals know, so if your brother stayed in a village or monastery near the Tibet border, a local may have persuaded him to try to corss illegally, say for a brief visit. Again this is speculation, but you should make inquiries with the Chinese authorities.
Again I hope this turns out well.
Richard

Just want to bump this back to the head of the line. Maybe someone new or just coming on will catch it.

Contact the moderators Upendra by private message (andreas_at_lp and frankie_flowers) or send an email to community@lonelyplanet.com.
They just might kisten if a lot of TTers ask (maybe they would be kind enough to delete these posts too).
scoodly

Guideupendra,
Thanks a lot, I posted information about my brother on the forums you gave. Hope it will get more attention.
Also if anyone else knows any other place to share this information and could post it there, I would be very grateful.
Thank you for all your support in these difficult moments.

Dear Richard (rdccomments)
I think my brother had about 400-500 pounds. Not sure if that‘s a lot. As we come from a country where crime and especially theft rate is quite high and we normally have an instinct to behave carefully with money (like not keeping it all together in one place, not paying surrounded by many people), I don‘t believe my brother would have been an easy target on that, unless all tourists/foreigners are targeted.
Really thank you for your point on checking the records carefully as they may be mixed up and your suggestion to get his passport number. It will be really helpful, once I go there.
As I haven’t been in Nepal myself before all advice on Nepalese culture or customs, that may make the search easier, or at least less troublesome, would be greatly appreciated too.