We know that the Longbottoms and the Potters were in the Order of the Phoenix. The Longbottoms were aurors but what were the Potters? That is the big mystery. What could they have done to trice defy Voldemort?
I think that James Potter was a target for the death eaters because he was very powerful, a pure blood, but refused to join.
Lily's wand was supposed to be good for charm work. I wonder if she might have worked as a charm breaker for Gringotts like Bill does. James, I wonder if he was an auror.
Who knows James or Lily could have been a teacher.
It could be that Voldemort wanted them because they were close to Dumbledore and he wanted to weaken Dumbledores defences before facing him, as would have been the final outcome, eventually. With less people to help him Dumbledore would be easyier to defeat.
"there's only one way to win a war: shout, shout, and shout again!" - The Duke of Wellington ((Blackadder - Stephen Fry))
It does make you wonder. We know that James was the smartest boy in school and the most powerful. You have to wonder what he did for the Order of the Phoenix.
The spell to protect Harry only works with someone who has his mother's blood. Even if Dumbledore had been related to the Potters, Potter blood doesn't count. Just Evans.
"You're disturbing...yet intriguing. Like couscous. I'm gonna call you Couscous from now on."