I have different group of cat families at my home. How do I unite them? One of them always fight each other.?

You've created the problem by having so many cats at your house. Some cats will never get along with others. Cats are solitary creatures and don't like to be surrounded by other cats. I have three cats at home but they are sisters and have been together since birth so they get along just fine. I would never get any more cats because I know my cats would not accept a stranger and why put them and the new cat in that kind of situation.

Don't get any more cats and spay or neuter the ones you have. If the problem continues, you may have to give up some of your cats or they will make each other's lives and yours miserable. It's never good to have so many animals in one home. This can lead to fights, disease, and hygiene problems not just for them but for you too and really can you afford vet care and food for all the animals? You are not helping them by having so many. Right now because of the tension and stress among the different families, their quality of life is poor and will stay that way for the rest of their lives unless you change the situation. Imagine 10-15 people living together in one place. It would be complete chaos. It’s the same way with cats.

This is natural cat territoriality behavior. The fact that there is a family of cats staking out territory makes the situation even more difficult to overcome.

Are you sure you don't have more cats that you can deal with, since you mention multiple families of cats.?