depend on the size of your percula and the size of the tank.
if your tank is 100g+ you shouldn't have any problem of keeping 2 sets of clown fish in it.However,do keep in mind all clown fish are very teritorial, it will really depend on the personality of the fish have.If they don't get along and being"selfish" on their teritory, doesn't matter how big of the tank u have they will fight over with each other.Sometimes providing the correct anemone will help, but again pure luck on that cuz most clown fish do share the same type anemone as their home.
I have 2 small mated true percula, they got chased around by 2 of my clarkii all the time, when i introduce a ritteri into my tank, those 2 percula got right into it and start to defending it. and clarkii is running away from them so that would be an example for you.