There might be food that they can get to or places to sleep. I had that problem and i really didn't care but when they get comfortable they stay around until they find a new place or pass
Your house has some kind of an aroma to it. Either that or someone feeds it. Once you feed it, it won't go away.
Copied and pasted of Google Search: If you have several stray cats on your porch (for just one day) it is probably because they are attracted to something in particular whether inside the house or outside. If the cats stay there and gradually more cats come over over the days, you'll probably have to figure out the problem and search your yard for anything that may trigger the cats interest. Otherwise spray the porch.
Many of the stray cats found in the school yard were taken to the local animal shelter so they could be adopted.
The problem may be numerous amounts of birds or rodents, attracting the cats. If you have a bird feeder that would probably be one source of the problem.
There are multiple solutions to your problem.You could bring the cats and kittens to an animal shelter or build a fence.
I heard that if you put some ground up hot peppers in a spray bottle full of water, and spray it around the outside of your yard, the cats won't want to go near it.
It is usually stray. That's what many would call a junk yard dog...
Cat Fences prevent cats from escaping the yard or anywhere and getting lost. This way, one can keep an eye on their cats and make sure they stay safe.
If he has kittens of his own he should not be hissing at all at them. Just get the kittens to leave the male alone. Always stay in the room when they are together and dont let them to close together. Sometimes you should try making the male feel so special. I have a female cat and she doesnt hiss at any cats exept for if they are in my garden or house. He is just defending his home he will get used to it.
There are sprays available at any pet store that you can use in your yard to discourage cats from wandering in your yard.
Honestly, most cats, if you ignore them, will eventually come to you. If they see you don't care they will come. If they think you care they will give you the cold shoulder. That is the nature of cats :)
Because they can be fatal if ingested, mothballs are not a safe choice to deter cats. Two safer alternatives are vinegar and ammonia.
I can tell you of how my aunt got a stray cat to have kittens in her yard. There was a beautiful stray Maine coon that was always prancing in her yard. Obsessed about the cat, my aunt put out some cat food for a week in the hope that she could tame her. The cat came around more often. She then placed the food closer to her house and started to interact with the cat. The Maine coon got so comfortable with her that she was able to take food from her hand. Soon my aunt set up a little house filled with soft pillows for the cat and left the food beside that instead. The Maine coon started sleeping in the little house. Before you know it the Maine coon had made the little house into a den for her baby kittens. Cats won't have kittens in a place where they aren't comfortable, so try to make them fell at home. Good luck!