This is not true in my experience...in fact the opposite seems true. For my cats once they've had a litter they can be much more determined and assertive in personality so you just might end up with more issues than less. I recommend you spay them asap.I have not even heard of them. What do they do? My mom doesn't want to spay them until
they have one litter apparently it mellows them out or something?
Another thing to consider is how you are cleaning up the pee and poop... as well as what litter and litterboxes you are using. A good enzyme cleaner is essential, and not using bleach or ammonia-based cleaning products. Many folk think they need to clean with bleach to make it sanitary but it can often attract a cat to pee where the trace odor of bleach remains. So use bleach on your litterboxes only! Maybe try Cat Attract litter in your boxes and make sure they are large and uncovered boxes and that you have more than one available and even in more than one location in the house. As Paige says, there is already a lot of information on this forum about litterbox issues...