That's really unusual, they really have to be provoked to breed and they will usually eat the fry (Babies) afterwards.
Gold fish breed easily, but for success you need a medium for the eggs and little ones to hide in or- munch munch You can buy "mops" for this. Usually if you want the young you would put them in a separate tank after breeding. You can see the male chase the female around the pond and try to sqeeze her against the side of the pond or a rock. I was just watching mine do this a couple of days ago.
The parents actually died before Tue babies hatched. I had five fish. They all.died at once so I'm guessing mmy filter failed. A few weeks later I was going to dump the tank and redo it when I.found tons.of babies
Update; babies are alive and well. Been about 6 or 7 months i think since i noticed them. Not too many deaths. I have like 30 of them? Theu grow fast. Theu are almost as big as the parrents i bought already Sent from my LG-E739 using Grasscity Forum mobile app