To get two cats close, you need to make the cat familiar with the environment and its owner. Don’t let the two cats come into contact directly to avoid conflicts. Then let the two cats start to contact slowly, and you can give the two cats something that is stained with smell to each other, so that the cats can slowly become familiar with each other's smell. Toys, containers for drinking water and bowls for eating need to be separated to ensure fairness. The owner should also play with the cat more to help establish a friendly relationship between the cat.
If you are two adult cats, first of all, don't let the two cats look at each other, so that they can suddenly find that there is an extra cat at home, or let the other cats find that there is a cat here. What you need to do is to put them in different rooms first, and you can open the door a little bit, first let each other know that there is another cat, so that the two cats can know that there is another cat, so that they can cover the door without letting them meet suddenly, and then slowly let them adapt, and then adapt to a certain level. If the two of them do not have that kind of warning cry, then they can meet slowly. If you mix it up, you can let them eat separately, or use two cat litter boxes to get to know each other first, then slowly accept each other, and then slowly get along with each other.
If it is a kitten, generally speaking, as long as the big cat at home and the indigenous people have no opinions, the kitten should be able to integrate into their lives soon. If the big cat wants to get rid of the fierce kittens, you can just separate them first, slowly let them adapt, and then accept each other, so that you can slowly get familiar with each other and live together.