I am fine with wanting twins. That's all good. This is the place for that.
I have no problem with that. I was only responding to the reason you gave that it would make it faster to get her out of the Astral Plane. You only need Kinu. If you want to add on to your reasoning, that it makes it faster to reach 32, that's true, but it's also an achievement and a challenge and meant to take effort. Whether people care about the effort and journey is their call. If the reason is: the story is canonically too short to have 32 kits, well... no one (except Savin) says that it's supposed to. Or even 15. The truth is that the story is canonically in too short of a time frame for any conception to birth that isn't supernatural or... like eggs in your butt.
As for whether kitsune normally have twins, I don't think it's any more normal than humans. Unlike humans, kitsunes are a race that feeds on life force. Obviously the mother needs to feed on more people with more kits (Champ's chi is... a special case, I believe. Very potent) and just like vampires are (or should) be circumspect in just creating more predators that feed on people around them, it is a slightly bigger issue, because starving kitsune turn into bestial abominations.
TL/DR
I was only responding to your reasoning in the original post. If The Observer or anyone else writes or adds a random parser to her birth scene where two or more pop out, it's not going to make me not absolutely love my kitsune princess. I am not gonna kick her in the stomach if she's like, "Beloved, I am having twins."
But if the reasoning is, I want 32 kids really fast, I don't think it's a priority (but I am just a guy sharing their thoughts here with you.)