house elf questions

[jwcpgh]

No: HPFGUIDX 77653

As I was rereading OoP and wanting to have that wretched Kreachur 
join his relatives on the wall of Grimmauld Place, some questions 
about house elves crossed my mind.  I went back and looked in the 
archives, the Lexicon and the Fantastic Posts but I didn't find 
answers.  However, I didn't go all the way back to the beginning of 
the archive, so if these questions have been discussed and resolved 
in the past, please forgive me for bringing them up again.

Where do house elves come from?  How long do they live?  How do they 
reproduce, that is, do they marry or pair off in some other way?  How 
does a family acquire one?  Are there house elves without families 
(or family substitutes, like Hogwarts)?  

Some of the posts in the archive suggested parallels between house 
elves and other elves in literature-Tolkien's, for instance.  But I 
don't see the comparison, really-they are entirely different sorts of 
beings.  (What do Legolas and Dobby have in common, after all?) 

Any ideas?

Laura