Math people... how rare is this?

[Kobi]

I just had one of my nichelings have twins. One's albino, the other's melanistic. How rare is this? Both parents had both on recessive.

https://steamcommunity.com/sharedfiles/filedetails/?id=2429184005

[Mickmane]

Depends on the parents. They need to have the right genes. :)

[Star 'Sword Sage' Sil]

Both parents have an independent chance of 1/2 of giving Albinism/Melanism. Thus, there's a 25% chance of a child having either one.

That said, the chances of Albinism v. Melanism are affected by if one of them can dominate over the other, which I remember being possible. I don't remember which one it is, but either way there's an 18.75% chance of whichever one is recessive under the other being expressed.

Assuming the twins have their genes chosen independently, we can multiply 18.75% and 25% to get a 4.69% chance of two children from the same parents having Albinism and Melanism.

Note that this probability doesn't take into account the fact that identical twins are a feature in Niche, nor the chance of having twins in general.