All of the Mons in my HG party apparently had the same ID. I wanted to breed my Espeon with a Ditto but since they have the same ID, they'd have only 20% percent chance to have an egg, since "They don't seem to like each other very much". Why's this? Are IDs not randomized in HG? Are they set to the same number? Am I luckily unlucky? All of my Party Pokemon's ID is 35896
The ID of a Pokemon is the trainer ID, so no matter how many resets you do, you will always get the same IDs unless you trade. Both in game trades and actual trainer trades are satisfied.
hope this helps.