https://www.fimfiction.net/group/211215/story-idea/thread/404887/repopulating-the-world-of-alicorn#comment/6883005

Where when you become an Alicorn (a mortal one), any kid you have, what ever the other parents are will be also be a mortal Alicorn, ever if the other parent isn't a pony, they become a Alicorn with traits of the other race.

So the story is about a Male Alicorn and there's a Cult of mares, who wants to have his child jest to bring up the numbers of alicorns up.