Answering my thirty-ninth question!
Sometimes, even I honestly get confused when having to draw them. "Is Tara the one with-? Yeah, wait. Let me go check her ref and old art.." "Now, for Tina, didn't she-? Yeah, it's supposed to look like that."
Although that's usually why I give Tara a blue shirt and Tina a green one, to clearly separate them. Although sometimes I don't make it as clear, I purposefully brought out the differences in them for this:
Breast size (of course)
Tara has longer hair than Tina. Tara's hair pointy-thingy on her head is also slightly thicker.
Tara has a more rounded chin, while Tina's is more pointy.
Tara's muzzle is supposed to be slightly thicker. (Barely noticeable though)
Tara's nose is slightly bigger.
Tina has more eyelashes than Tara.
Tina's floofs on the side of her head are smaller than Tara's
Tara is slightly taller than Tina.
So hopefully now you'll be able to tell them apart. "But Wolfie! In this old art here, it's hard to even tell!" Well, that's why I'm getting better now. This year is going to be me trying to make sure each character doesn't have a same-face (most of the time) and can be told who is who just at a glance. (Although it'll still probably be hard for these two since they're twins.)