Male Siamese Urinating

Okay, my male siamese, Pippin, is urinating on my boyfriends clothes and some other random stuff, but he goes in the litter box most of the time. We thought he was doing it on the closet floor, but realized he was doing it on my boyfriends dirty clothes in the hamper, so we started keeping the door closed to the closet, but i saw this morning he did it again on the clean whites in a basket on the floor. He paws through the clothes and pees on my boyfriends shirts and/or pants. It's so weird! He did this once on my black slacks where we used to live and my boyfriend just informed me that he noticed that some clean curtains I had in a basket on the floor had old urine on them.

The only changes we have had is that we moved in with my boyfriend to a new apt. in May. We had already taken in my female tabby, Barbie. They became close friends fast and love to play and bathe each other. Pippin has even lost some weight b/c they play so much! So, do you think Pippin is competing with my boyfriend or crying out for attention? Or, just competing with Barbie? What do I do??? HELP!