Our kittens are now 4 months old. They were dumped on a doorstep at 2 days old and were hand-reared by a friend. The female is a star - we've never had an issue with her - she came to us litter trained and even when she had a dodgy tummy she never had an accident. The male (who is by far the most cuddly of the two!) is a bit of a nightmare. He wees all over the place. His favourite things to wee on are carrier bags and fabric (particularly washing of any variety). He's currently banned from the bedroom (along with his poor sister) -he managed to get in yesterday and do a big wee on the bed and one on my pillow.
So far we've tried: feliway (both plug in and spray), three different types of litter tray in three different rooms, several types of litter (both non-clumping and the corn based clumping sort), keeping them in one room with the litter tray (he still pee-ed whereever). He's been to the vets who couldn't find any issues (and it's not little bits of wee he's doing - it's full bladder emptying). He wees on the bath mat which is right next to the litter tray so he's not getting caught short.
What do we try next? I'm sure he's extra cuddly just to make sure I love him too much to get cross about the wee that's slowly taking over my poor house!!!!