From Pokemon Fusion Wiki
Below is a short rundown of how relationships between the various species function in regards to breeding and societal views.
- Human + Human: This is to be expected, unless of course you are a nerd.
- Human + Fusion: While taboo surrounds these couples worldwide, there is some lingering doubts of the ethics for those couples who defy the odds. Unions of this sort can produce both natural-born fusion offspring as well as human children. Human/Fusion relationships are often featured prominently in IC media, particularly romance and drama, and range in social acceptability from perfectly normal to romanticized to prejudiced against depending on region and demographics.
- Fusion + Fusion: Acceptable interaction in most regions, potentially awkward due to sizes and body shapes. Result will generally be natural-born fusion of course. The pair is capable of bearing human offspring, though it is generally more difficult and uncommon than when one parent is true human. It is not uncommon to see a human child with two fusion parents, because of this.
- Fusion or Human + anything else: It is seen as bestiality for humans and fusions to cavort with Pokemon, thus obviously being a cultural taboo in Kasei as most other places. No offspring are possible for either.