These are ‘teenage’ Herons. Still in the nest and probably eating non stop.
I bet the taller, and first born, has actually taken his first test flights.
I have seen young birds stay at the nest for a long time.
After they fly, the real work starts. They must learn to hunt. They will move around the rookery, learning to fish. But that takes time so young birds return for a meal while still figuring out life.