Importing data with households
Your dedupe rules aren't probably tight enough so instead of seeing that the contact exists already, it creates a new one.  

The fact that your getting dups also probably says you are doing multiple imports with the same CVS.  When I do imports I often do run the same file more than once, but the key difference is if the contact already exists and you are say adding them to a household, you should check the update box on the import instead of the default.

So having said all that, if I'm importing new hh and individuals and trying to create the relationships, I will import the hh and ind and give them an external id.  The external id can be anything, number, letters, a combination.  Then I use that external id as the link for creating the relationships, importing contributions, etc.  The external id has to be unique unlike names and email so it won't create new contacts when it doesn't match like it does with just names.