the Prophecy Harry and James as Voldemort's targets

[kateydidnt2002]

No: HPFGUIDX 75203

Ok, in OotP we find out that Voldemort wanted to kill Harry because 
of Trelawney's first prophecy. 
So why did Voldemort want to kill James? In SS p294 Voldemort says "I 
killed your father first, and he put up a courageous fight...but your 
mother needn't have died..." and in book three Harry hears Voldemort 
saying "Stand aside, stupid girl!" (or something to that effect-not 
looking at my book at the moment)
I have always thought that this meant that Voldemort went there that 
night specifically intending on killing both James and Harry, and 
Lily didn't really matter. Yet the prophecy only indicates Harry as 
the threat, so, logically, Harry should be the only target.  I assume 
that the part that was overheard and communicated to Voldemort 
was: "The one with the power to vanquish the- Dark Lord approaches
 
born to those who have thrice defied him, born as the seventh month 
dies" (This is because Voldemort had to have that much information in 
order to narrow the choice of who it was referring to down to Harry 
and Neville and I wonder if he heard more, confirming that it was 
male or if there were females who also fit the parameters if he heard 
none of the masculine pronouns) This indicates only one individual to 
be his opponent-the one who is the son of two people who have defied 
Voldemort three times and born at the end of July.  It says nothing 
about the individuals father being a particular threat. So why was 
James a target?
If Voldemort wished to kill James simply because he was a strong 
Dumbledore supporter or strong opponent to Voldemort wouldn't he have 
wanted to kill Lily too because she was just as opposed to Voldemort 
OotP (or rather the prophecy) indicates that BOTH Lily and James 
defied Voldemort three times indicating, again to me, that Lily was 
as dangerous an opponent as her husband. So why would Voldemort be so 
intent on killing James and not Lily when both seemed to be working 
hard against him and Harry was the only one mentioned in the prophecy?
Random theory on killing James and not Lily-perhaps at the request of 
Wormtail?
If this specific question has been addressed, I apologize and ask 
that you please direct me to the appropriate posts.
Thanks!
Kateydidnt