Hi! Do you mean kissing on the mouth or kissing/nudging other parts of the body? I have never seen goldfish kiss each other on the mouth but anything is possible and goldfish are very social creatures. 'Kissing' or nudging other parts of the body is classic breeding behavior. Breeding behaviors can become aggressive, so keep an eye on everybody and seperate the parties if one is being overly harrassed, stressed or injured.
Yes, they actually "kiss" on the mouth. I'm not sure the sex on either fish, but I am worried it was more of a dominance thing because I just bought the one calico fish and put in the tank that day. They wouldn't breed so quickly, would they?