It's on the pokédex pages. And Tauros and Miltank aren't related at all.I just was looking at the gender mechanics page due to the update mentioned in today's news and then checked the breeding mechanics page. Neither page discusses paired single-gender Pokémon. By which I mean Pokémon which share parentage for breeding purposes (in the sense that eggs will hatch into one of two species depending on the gender of the hatched Pokémon), i.e. the Nidorans, Tauros/Miltank, Volbeat/Illumise, etc. I feel like this would be valuable information to include on either the gender or breeding mechanics page (or both) as this factor isn't always apparent.