I know what you mean, but I have 3 hearts with Bernard, 1 heart with Arion, 1 Xer, 1 Rhot and 1 with Korg and I did't break no one's heart (literally and metaphorically). You can have hearts with anybody you want.
I think right now you can only progress to 3 hearts with Bernard? To me 1 heart feels like just getting out of friend zone. I'm not sure what would happen if you get 3 hearts with two or more NPCs in the future. And I think the chance of they're all into polyamory is low......
