Who peed on the rug?

I adopted a male neutered cat in Feb., he is about one year old. He was extremely timid and spent most of the time under the bed. He trusted me, I talked softly to him, and we had a routine he was somewhat playful.  Several months later, I thought Barney would enjoy the company of another cat to be his friend and play. She was 7 months old, very affectionate and playful. Barney hasn't warmed up to her. She jumps up on the bed next to him and he will not look at her or he jumps off the bed.  She may be a bit aggressive in her play. He was a sweet gentleman, but now he seems very withdrawn, won't play, and doesn't want to be touched. Every time I talk to him (he likes that) she runs in the room and gets in the way.

Someone peed on the bathroom rug. I washed the rug, put it back down and it happened again right away. I don't know which one of the cats did this.  I can't believe sweet  Barney, who has good manners for a cat would have done this. I don't know which cat to take to the vet.

Is the rug the only soiled item? You need to use the proper cleanser for getting rid of the smell of urine or feces. Just washing the rug with regular detergents is not enough. Look for enzymatic cleaners available in pet stores. You can also google for homemade urine removers using white vinegar and baking soda. Cats have very acute sense of smell. Either Barney or his new girl friend could have peed there if they smelled even a trace of urine. 

How many litter boxes do you have? Perhaps whoever urinated on the rug, had no access to a box?