See Creeper
The vast majority of creeperkin are not 'born' so much as 'grown'. At first, a newly-embedded creeper spore doesn't look like much of anything--just a red, itching welt in skin freshly-healed from an explosion, and entirely unremarkable compared to the injuries that preceded it. The vast majority of embedded spores will be killed by the host's own immune system; failing that, more aggressive methods such as burning or even amputating the effected limb will generally do the job. Very rarely, however, the spore will stay put and begin to grow, feeding on the rich nutrients supplied by the host's body. As it develops, this takes a toll on the host, starting with fatigue and anemia and progressing to severe malnutrition and, in most cases, death. By this point, the creeperkin has developed enough to no longer require such a rich and constant feed of nutrients and can technically survive on their own, although they are still very fragile.
Needless to say, such a gruesome origin story doesn't exactly endear them to other species. While that's hardly their fault (all of this happens before they're even properly conscious), they tend not to be well-liked
On a less disturbing note, creeperkin can also be born to two creeperkin parents, and in this situation their development happens exactly as it does for most other species. Considering how rare the species is, this is even more uncommon, generally limited to the tiny, isolated all-creeperkin communities that hide in far-flung parts of the world.