Babs
Good day

Regarding egg laying when kids are still in the nest, It's not unusual.
Most of my guys will start another clutch right before, or right after the kids fledge.
If I don't want another clutch, I will either remove the nest box right after the kids fledge, or remove eggs and block the nest box, disallowing them access into it.
If you want another clutch, then just let them be. This is a good learning experience for the kids. They learn about egg laying, incubating, hatching , and caring for the hatchlings.
If the parents allow it, the kids will help incubate, and later will even help feed their siblings once they hatch.