The OP is not asking about finding Pokemon that are capable of breeding together. They are asking about how well compatible Pokemon will like each other. Ex the different things the daycare helper will say about your Pokemon. "They don't seem to like each other very much..." vs "They're completely inseparable!". All of which correlate to the % chance an egg will be produced each egg cycle.
As for an answer to the question.... I don't know (though would be very interested to find out). However, obtaining the Oval Charm for completing the local Pokedex is very helpful, as it shifts the % brackets for obtaining an egg by some amount.