I have 2 kittens about 4 months old.  I got them from the pound, but
they're not related.  The male uses the box no problem.  The female
won't get near it.  She prefers beds, clothes, sheets, floors, etc.
Poop and pee go everywhere but the box.

I only have one box.  Could the male have "claimed" it?

I've seen a lot of remedies that envolve watching the cat, but it's
just not practical.  We've got kids and activities and all such
things, and keeping a constant eye on a cat that may or not pee.
We've got lots of places for her to hide.

We use clumping litter "Worlds Best" or some such thing that I read is
the best to get.

My wife is getting fed up with these cats (I was the one more
motivated to get them), I'd better do something or the female is going
to get tossed out!