Two (overworld) nether portals, over 500 blocks away connect to same (nether) nether portal, and leaving the nether results in teleportation to first (overworld) portal built. Tested in survival and creative, varying ranges from 100 blocks to 1000, all present the same problem of connecting to first portal. Instead of getting 2 overworld 2 nether, gets 2 overworld 1 nether.

Edit: any additional overworld portal created will always connect to the first overworld portal created