I have 2 standard male doxies. They are almost 5 years old and our brothers. They are both fixed. Back in January we got a female mini longhair doxie. The boys have all of the sudden stated marking things in the house over the past month and a half. We have 3 floors in my house and the female has only been on one floor. Yet the boys are marking on all 3 floors. We use to be able to leave them out while we would be gone but now we have to put them in there cage. The female was just fixed this past week. She is almost 6 months old. Im pretty sure they are doing it because of the new addition to the family. What can I do to stop this? My wife and I have had it with this behavior. Thanks in advance.