We've collected our new kittens today, imaginatively named Sandy and Mittens by the kids. Sandy initially had a quick explore, then settled himself under the sofa, and hasn't come out...apart from to find a dark corner and wee under a box. I quickly cleaned it up and wiped the floor with a litter box disinfctant wipe. I'm worried though that he now thinks that corner is his toilet. We have no experience of kittens, and have been reading up as much as we can. Should I put his litter tray there...but then the other kitten might not know where it is, and she's already used it. Help!