Hey, can I just remind you that the ROTJ novel is NOT EU! Under no circumstances can it EVER be EU, no matter what. It can be wrong, but not EU.
Remember, EU is not code for 'wrong', but simply defines those parts of Star Wars that are not directly spun from GL's writing. The ROTJ novel IS spun from GL, so it is not, and never will be, EU.
And it so happens that EU is not canoncial. But it does not follow that everything that is non-canonical is also EU.
And may I remind you that, according to Lucasfilm, the ROTJ novel IS canonical (well, 'semi-canonical', anyway). However, it will be totally overridden by the coming film as far as the Owen Lars/Obi-Wan's brother bit is concerned, as per canon rules that put the movies above all else.
Meanwhile, far more direct proof of the original plan of having Own as Obi-Wan's brother is that it was originally scripted. However, when it came to making the story I doubt it made much sense; having both of them from Tatooine stretched it a bit.
What? That it had been sold to Gardulla the Hutt? I dunno, vague answer to Padme's question then....
I personally think from an OT point of view, Owen being OB1's brother makes a lot of sense. That'd be the reason why Luke was there: OB1's home planet, backward, out of the way, controlled by the hutts. His and Owen's oufit looked very much the same as if that was a farmer's outfit.
Now with TPM that perception is gone. Those clothes are now official Jedi outfit (I doubt that they were during filming ANH), Tatooine is not controlled by the Republic and therefore a potential Jedi could not come from Tatooine. So OB1 could not be a Jedi.
But with Anakin from a totally different planet, GL would not have to go through all this complex storytelling to fix the holes. Anakin being born without a father, lives on Tatooine, mother marries Cliegg Lars who already has a son Owen, hence Owen being Anakin's stepbrother.... a lot of communication about family members.... does not do well for storytelling IMHO.