Nature vs. Nuture

I don't know too many parents with more than one child who would say any one of them are the same.  Perhaps if you have 3 or 4 children you might say two of them are similar but odds are if you only have two children they are polar opposites.  My boys are so different personality wise I've pondered the nature vs. nuture question.  For example, Nick is more social and thoughtful.  He's the first one to ask you how your day is the minute you get home from work.  If you've been sick, he'll ask you how you feel.  If you do something nice for him he'll usually say thank you without being prompted.  This casual chit chat does not come natural to Jay.  With the passage of time he's improved.  On days when I've been sick and I tell him I can't do something for him because of it, his reaction is usually, "Huh, you're sick, for how long, I didn't know that."  Jay has friends and good ones at that but he'll be the first to tell you he really doesn't like people.  Nick, on the other hand, gets his energy from being around people.  I do not want to insinuate that this is a personality flaw with either one of my boys.  They each have their own strengths and weaknesses, like every other human on the planet.  Being quiet comes naturally to Jay.  Nick, not so much.  Jay knows when it's best to stop, be quiet and listen.  Nick is a work in progress in this area.  So what have I done differently with each of the boys?  Why is Nick more naturally thoughtful?  Why is Jay more naturally quiet?  Beats the heck out of me!  That's the way God made them.