Re: Poor Uncle Owen and Aunt Beru... Oh Well!
If you follow the EU then there were dozens (hundreds?) of Jedi who survived the initial implementation of Order 66, and Vader spent most of the time between the two trilogies hunting down the last of them. I'm not sure but I swear I remember reading somewhere that by the time of ANH he was closing in on the last few Jedi.
They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance. - Terry Pratchett, Equal Rites