There is a possibility that your John Sanderson's parents where Timothy Farrar Sanderson and Sarah Randall. I'm basing this purley only on this messege board post:http://boards.ancestry.com/localities.northam.usa.states.new...
I've been looking for proof, but I need a little more to say this is it for sure. My guess is that John's middle name was Farrar. So far I'm not finding any confirmation.
Additionally, my John Sanderson (which I'm thinking is the same as yours)had a brother Josephus, who also moved to Wisconsin sometime between 1847 and 1850.