Hi everyone. I'm asking this question for a co-worker. He has 3 male cats. He adopted two of the cats about 7 months ago. I think that they are still under 1 year old. The other cat is about 7-8 years old. For the past 2 months one of the younger cats has been peeing and pooping in the bathroom sink. He said that the other day they had company over and the cat did it right in front of them. Have any of you ever had this problem before? Do you know what might be causing the cat to do this?

I told him that it might be because the litterbox is too dirty for him. He had also thought of that too. I think that he only has one litterbox. I also told him that he might want to try to train the cat to use the toilet. He thought that would be a great idea. Thank you in advance.