let sb in

Hello,

Think of three lads in a photo. Two of them are well built, good looking and stronger. But the third young man (that's me!) doesn't look so. He looks much too skinny!

I showed this photo to my friend, who is a native speaker of English and got this reply:

• 
  
  '' But you are skinny... they let you in ?
  
   ''
  
  
  (i) Now, what does let sb in mean?
  
  
  (ii) Does that mean ''will you let them be superior than you?'' OR what?
  
  
  (iii) Do you think let sb in can be used accurately there? 
  
  If not, what would be the exact phrase or expression that YOU would use instead?