Does Kitt-Kat hate my daughter ?!?!

Okie, I've had my huge male siamese Kitt for a little over 6 years now and yes, there have been some major life adjusting issues for him lately like my daughter moving back in with my 13 month old grandson. BUT....they have been here for over 6 months and both cats seemed as though they adjusted very well. Well, the other day Kitt my siamese starts using the middle of my daughters bed as his litterbox sorta, he still urinates in his litterbox ?? We got everything changed and later that evening my grandson was taking his nap on the same bed and Kitt repeats his earlier dirty deed while my grandson was sleeping there !!!! Ofcourse he got the usual water bottle spray since I actually caught him in the act but this still has not stopped him and he is quite terrified of that water bottle.....
I have no clue as to why he started this behavior nor how to stop him. ANY advice would be most helpful.

Inappropriate peeing should be checked out for medical problems. If a clean bill of health is given, then its more of a behavior problem.

Especially in males you don't want to wait around if he has a UTI - do that first before trying to figure out behavior problems.

I had a houseguest for a couple of months that was not too fond of cats at first. One of my cats started doing the same thing on his bed. For some reason, the houseguest grew to like my kitties and it stopped.
When I first asked my vet about this, the vet thought it was because things were 'out of order' because all of a sudden, a new person was there. Who knows?

I just wanted to second the advice about checking for a health problem first. UTI's in male cats can come on suddenly in cats who've never had health problems before and can be fatal. You want to rule that out ASAP, particularly if you see blood in the urine, small spots of urine in inappropriate places or you see you cat straining but nothing comes out. All of those signs mean you need to get to the vet 10 minutes ago.

First, please stop spraying him with water. There is a reason why he has suddenly started using something other than the litterbox for his business. The solution is to find and deal with the reason. Squirting him with water isn't going to accomplish that.

As the others have said you must first rule out a medical problem. This is the #1 cause of going outside the litter box.

Also, see this thread:

http://www.thecatsite.com/forums/showthread.php?t=22301

I would get him to the Vet ASAP, to rule out medical problem before you try other measures.

Thank you all for being so concerned about my baby Kitt-Kat but as I explained in my beginning post he is not urinating elsewhere {or having trouble doing either} he's randomly started let's say...."doing his dirty jobs" outside his box and only on my daughter's bed and usually only when they are here at home with me....Even his vet thought this was an odd behavior from Kitt personally because she's treated him since the age of 6 weeks old, know's his demeanor, his "training" and most importantly know's Kitt's health history and Kitt is blessed with a current health status, which is remarkable.
I was very hopeful that someone here had either been through this with thier own or perhaps knew of someone who had because this needs to be resolved to ensure tranquillity within my home. I know Kitt has something he's trying to make loud and clear and in his mind he's doing exactly that..
Hopefully I have given you a better understanding now of the situation and here together joined by others a possible idea of what my alphamale is trying to say will unfold....
Thank you all very much for your time....

)0(

Thank you for your input....I have fears of Kitt not approving of mainly my grandson being here only because he is just now walking and demands much of my attention, the attention Kitt also demands. Now I do make certain I also take extra special time for both cats each day, however they have had me basically all to themselves until this tiny, kind loud human appeared....

He's staking out his territory the only way he knows how, but you obviously can't let it go on, so for starters (til things are normal again) I'd throw some big plastic sheets over the beds (he won't like that much) - maybe a mattress co. will give you a couple. Would it be possible if only for even a week or two to keep that door closed apart from coming and going? It will at least discourage him from going on the bed, though whether he goes somewhere else besides the box is ??? Try getting him a cat tree with his own perch on top (the higher the better!) and distract him with his new 'toy'.