We tend to refer to spiritually advanced people as "old souls"(although of course all souls are really the same age, probably unlimited).  It is something about their personality and their approach to things.

It isn't or at least is not entirely a matter of interest in religion; indeed they may even be anti-religious in the usual sense of organizations.  Nor is it gullibility (those who tend to think "belief" and faith are important, or who want so much for the universe to be a big kindly teddy bear).  They tend to know and do the right thing automatically, without thinking about it and without goodness motives.  They tend to nod and find something in whatever you say that they can agree with, and reinforce that rather than getting negative.  Indeed they seem inherently happy no matter what.