according to the well, making "half folk" requires the very complex and exotic ritual of casting the pregnancy spell:
"Through the blessings of the Nandan subcult of Ernalda, it is possible for someone to bear a child to term even if that would not normally be biologically possible. One consequence of this is the possibility for different mortal species to have a child together – humans and aldryami or dwarfs, etc.
This may be the source of both Pavis Half-Elf, and of his daughter with the dwarf Flintnail. Such combinations are always unusual and remarkable, an echo of the God Time. It is worth noting that Lord Pavis Half-Elf dates to around the time that the Beast People first appeared in Dragon Pass. It could well be that in the Empire of the Wyrms Friends fertility cults as Nandan were strongly supported by the Third Council of Dragon Pass as part of the Great Ritual."
https://wellofdaliath.chaosium.com/half-folk/