I have a 4 year old Siamese Female who has gradually began and continued a horrible habit. In my old house she would just pee in my dirty clothes hamper but I successfully broke her of that habit. I had to move her down to my parents for the summer because I was unfortunately going to be out of town for a job and studying in Italy.
During the winter when she met our dog she wasn't pleased with him and I can understand why she started peeing/spraying on my things...So I just recently returned from Italy and she has been here awhile and now seems to be getting along fine with the dog but has started to pee all over my things. i have never caught her before but now I am catching her all the time. I know this behavior is due to a breach in her territory and that she is jealous of the dog as much as he is jealous of her.
I read that you can just give them their own territory (and Siamese love their territory) and that you can get them to just spray or pee in the litter box instead. How?!
Answer on How do I teach my cat to stop spraying/ peeing?
she being territorial ... claiming you as hers. get a spray bottle filled with water and each time u catch here doing it give her squirts. cats dont like it. i have a male cat that claims me when i sit outside ....... he is slowly learning its a no no with the help of the waterspray