Not all too surprising in theory since it was likely stress induced birth. I never tried to breed fish before nor do I plan to in the future. If it happens great, if not, cool.
As for aggression I have little to none in the tank. 125 gallon, 1 full grown stonii and a mix of smaller malawi cichlids. Total count is 7 fish. Been with me for 6 to 8 months with the only problem being the one time the common pleco ate the stonii that was laying on its side stalking its prey.