Simple answer is to be brief-Read its commentary:
When souls were created,some found affinity with each other &some didn't. Souls are of two types -good souls & bad souls .
When you come to this world, you recognize those with your type "characteristics" habits&goodness &you immediately recognize them !Though it doesn't mean that those friendships will last for years but a good impression is laid on the similar kinda soul&you remember such people!
Other than that you see someone at first &you don't recognize them or feel repelled ,it doesn't means they always bad or won't change .At times they change but basically, the "hadeeth'refers to people of same interests ,virtue, piety&qualities that makes them bonded... Like we see on forums/Twitter etc .We don't even know those people but by getting to know their view points, you get "my similar soul or twin soul"
At the same time you recognize some people but you don't know them well & you think they are like you though they turn out to be somewhat different than what we perceived-Wrong type or not virtuous
Though both kind of people can change, bad into good but I'm not sure reading about pious because it's their fitrah&I'm talking of those pious people who turn towards Islam &occupy the good understanding of Deen with good qualities!
Also,as you say just by looking at some peoples face ,you get this siren in mind-No!
It happens ...
It alludes to an individual's Firasah(foresight) at times & such things.
Alhamdull'ILLAH!
[MENTION=40458]Simple_Person[/MENTION]