I read this book a few years ago, I really want to read it and some other stuff by the author.  So what's the problem you say, the problem is I can't remember the name of the book or the author

The book starts with this young boy hiding on a ship that's been taken over by someone, space pirates of some sort I think.  His family and most of the other people have been killed.  He gets found and forced to be a slave for years for the captain who killed his family.  He finally gets away when they are docked at a space station that is attacked by a race that humans have been at war with for years.  Only problem is he is captured by them.  Turns out these guys aren't as bad as he thought, they take care of him and train him to be a spy for them.  Eventually he is sent out to spy and he becomes a member of the crew of a human ship.  I can't remember anything more except that possibly he gets captured by the pirate again.

i think this might be Warchild by Karin Lowachee.  i read that about five years ago and had to go find its title in my book journal, since i couldn't remember either.  :)  i remembered the name Jos as soon as i read your description.