Quote Originally Posted by rinku
I don't know about that. I've got some pretty solid experience in breeding now, and I've never noticed nature having any effect on the message given (I'm not saying it has *no* effect on egg rate - that's much harder to determine). It's determined by species and original trainer:

Can't Breed = "They prefer playing with other pokémon"
Same Trainer, Different Species = "They don't seem to like each other"
Different Trainer or Same Species = "They seem to get along"
Different Trainer *and* Same Species = "They seem to get along very well"

Note that different evolutions do count as different species (as do Volbeat/Illumise)
Don't ask me.... I just say it in a guide once.... or maybe I dreamt it.