Never ever add a larger clown to a tank with an exhisting clown. It's begging for trouble. The larger fish (mated or not) will almost always be female, not male depending on age, even if solo. The best advice is always add the smallest specimen you can find and at the very least, Â½ the size of the incumbant fish.
The chances of introducing a second female is greatly reduced if the newcomer is quite small. It will typically still be male or even a nueter. If adding a larger fish, you will most likely be placing two females in the same tank which would be disasterous.