my cat whispering expertise here for 4k

change the place.. put your kittens in a place you dont care where they shit and let them grow a little more before let them access your home again.

I dont think the saying

"please refer to my sig" has ever been better used


*clears throat

Please refer to my sig

If you take them from their mom too early they will get brain damaged, they should be atleast 12 weeks old.
Dead mom? mom crap on the floor aswell?
mom not around?

They're around the mom and she poops in the litter box..
They watch her poop in the litter box..
Come on now... This shit is dumb!!!

Build a *wall* arround the litter box, and put a case in there, with something they can lay on
Don't make the wall higher than the mom can jump and make sure to give them a little space to walk on, also make sure to clean the litter box alot.

Hm, seems weird that every kitten does this, they should have learned how to use the litter box 2 weeks ago or so

is it a full sized contained litter box?

Like this:
http://www.yourpetscount.com/image_manager/attributes/image/image_5/41353356_9237797.JPG

if so, it might be an issue with the entrance being too high for them to be comfortable

try getting one of those disposable cooking trays that are only an inch or 2 tall and putting some litter in it, see if they're more inclined to use that