How I think twst genetics work~
Ok so here are the basic four:
Human, Merperson, beastman, fea.
My brain works a little weirdly so I think Merperson is like half human half fish. Beastman are half human and half animal.
Which means human technically works as a neutralizer in most cases.
So for the whole coupling together thing it's rather intressting.
For example the odds of a child being one or another is about 50/ 50 for most magic worlds.
Butt I think it's far more fun my way!
Hybrids are still rare there's like a 15% chance of having a hybrid.
Depending if it's a beastman or mermaid the chance of have a human with weaker animal or fish traits is higher.
And if it's fea and human the chances stay at about 42% for either or. And the normal 15 for a hybrid.
Beastman and merperson is a little difficult to keep up with sooo. Think about it like a pie chart each own 50% of their own board. Then mash them together, the animal and fish half then take about 25% each and the human part is at 50. Then you have to add the hybrid type which lowers even more.
I am aware that it doesn't make sense but I like how my mind works.