I think that it's more likely that your brother remembers stuff from FA because FA contains all the high yield stuff that you spend years learning, not simply because he read it from FA. For example, I could likely tell you most everything FA has to say about B. anthracis because I have learned about it numerous times, though I probably only looked at in in FA once. If your brother really can recite it verbatim though, that is a different story... He's crazy.
As for those people who didn't start "studying" until end of 2nd year, I think you are forgetting an important piece of information: The first 2 years of medical school aren't just a waste of time - They are designed to teach you the basic information necessary for becoming a good physician and doing well on step 1. Those students who do well in classes during the first 2 years have a solid grasp on the material, and only need a short time to review and refresh it before taking step 1. So they are essentially studying from the beginning as well.
Honestly, as a first year you are not going to have a good enough understanding of the material for FA to be of much use to you. FA is a horrible tool to learn from, it just contains high yield facts in outline format that are great for reviewing what you've already learned. Your best bet at this point is probably to do well in your classes and retain as much information as possible by not trying to cram right before a test. Going over FA after a given class is helpful too, as it helps solidify the info and exposes you to FA's format early.
I haven't yet taken step 1, so I can't really comment on what I would have done differently.
