Is the thing about halfkin potentially having an ordinary animal baby just flavor text? I've only had one give birth and I was hoping to get more dogs. Or pets in general, since the dogs seem completely useless.
Mechanically speaking, there are no animal characters in this game; the "animals" provided by the kennel for sex are simply temporary persons labeled as animals. Without mods the description "their offspring will often swing back to fully human or fully beast." is simply flavor text. The Aric's Expansion mod adds more flexibility to halfkin by allowing them to rarely produce beastkin, but there are still no animal characters in the game.