Why Is The Night King So Interested In Jon Snow? Theory Explained

 The dead people brought back at Hardhome were all wights, not white walkers. From the show, we know that Craster's sons all became WW. Don't know if WAY BACK in the past, the Night King also made female WW. I guess someone has to take care of the baby WWs, lol.

The Night king is interested In Jon Snow because the Night King is Brandon Stark, a STARK, and Jon Snow was the first STARK he saw when rising back up. Bran has gone back to fix the problems he created in a different body (Brans current disabled body) hence he knew about everything that happened up to date.