The difference between males and females in Fairies.

Due to the Males possessing one Dominant gene(X) and one other (y), They would naturally be weaker than the Females of the Race who held two Dominant genes (XX).

The other gene’s strength depends on the capacity of the mate that contributed it. Going purely from interracial pairings *

A witch is inherently weaker than the fairies, only wielding about 75% of their fairy counter part’s capacity.

Hence if a child was born from a fairy and witch (based on the assumption that the Fairy was at least of higher noble status) Then the child would probably end up as a lower noble ranked fairy. In terms of capacity alone.

The X gene of the fairies is able to ‘bond’ with other X genes and raise their efficiency which would make up for the total weakness of the human genes. It cannot do this with the Y gene which is why Female fairies are usually at a much higher capacity than their male counterparts regardless of inheritance.

If the child were borne to a human and fairy pairing the capacity would be completely reliant on the Fairy’s magic as humans cannot process magic at all.

That is why human to fairy pairings are usually only performed by high ranking nobles.

If the Fairy was a high ranking noble and had a child with a human, it would most likely inherit a capacity on the same level of a commoner fairy or a low ranking noble if it were lucky.

One would need at least a commoner’s worth of capacity to be able to survive in the other world. The other world has a very limited amount of oxygen and capacity to use magic is what determines if a being can survive in that world.

The children born of human and fairy pairings would need a certain level of power in order to both enter the other world and not die from the lack of oxygen as well as to have reproductive value. *(Hence, have enough magic to pass down to the next generation even with a weaker contributing partner)

If a complete human were to be brought over to the fairy world they would gradually turn into a stone-like state and be dead within the hour.

A commoner would not be able to bring back a child born with a human simply because there is no way that they would be able to grant the child a high enough capacity (With the inherited capacity being halved by the human gene donator).

Magic can be transferred, and magical capacity can be supplemented but these methods are often extremely dangerous and pricey which is another barrier stopping commoners from having children with humans.

This also means that since the Fae-Goblin wars there have been no commoner children born. As the two races are still rather distrustful of each other.