Should we separate older guppy babies from newborn baby guppies so they don eat each other?”
It is not just related to the mother and father guppies. Any larger guppy will eat smaller guppies. They don’t know the difference between fish food and other swimming things. I use a guppy breeding unit that hangs on the side of the tank. It has a V-slotted area for the mother. As soon as she has her babies, the babies drop through the slot. (babies don’t swim for about five minutes) so they drop to the bottom. As soon as the mother has her young, I put her back in the regular tank, remove the V-slot and let the babies stay in the breeding tank until they are large enough not to be eaten. I then move them to a tank with just guppies, because some other species of fish may still consider them small enough to be food. As the guppies grow into adulthood I reintroduce them back into the large tank.
