I'm really sorry about the loss of Kathlyn. She must have been an incredible friend.
I think your feelings and your introspection are healthy. My cat Max passed away in April of 2019, and it was just me and Tess for a while. She and Max never really got along, but I could tell she was lonely. So Hugo came home.
Hugo isn't Max, and I still miss him. I sometimes still ask Tess if she remembers him (but being a cat she doesn't answer). Hugo is curled up in my legs currently, and he's a nice boy. But I still miss Max.
Bringing him home came from a good place, and I'm sure you're right that getting kittens will be for you, too. I always like to think my cats wish they could still be here but are glad another cat in need has a home.