Okay. That is very different than saying a mated pair. I am not giving you a hard time, but explaining the difference with clowns because it is very important what stage the relationship is in.
Since they seem to be getting along. I assume one is larger than the other. The larger and first added should be the female. Now, if you add another ocellaris now, you risk the female choosing the new one and abusing and rejecting the current male. Happens.
Once they bond (stick together and hang out together) that is good. Then they will begin to consider mating. My occellaris are inseparable, but have not mated and they are about 1.5 years old or so. My skunks (nigripes) are that age, but they in general can take up to 4 years or more to lay eggs. Just the species. My percs are too young, but inseparable same with my clarkiis. No, these are not all in one system. The perc and clarkiis are in separate (clarkiis soon to go with the skunk and occellaris).
In a 65, I would say you should stick with one pair. Mainly because you will get some great mating behavior and not have to worry about other clowns bothering them. However, once they begin laying eggs, without a host, they will not let too many other fish into the system. So, try to get your fish added before this happens. :)