My niece and nephew have perfectly regular sleep schedules. As in their sleep schedules are super consistent.

Is it "regular" like "regular people have it"? Fuck no!

But their schedule is like clockwork with it's regularity.

Wake up at 4am, full of energy until 4pm, unconscious until 8pm, wide awake until midnight, asleep until 4am, repeat. They're 10 now and I really hope they get a job someday that let's them keep that kind of schedule because it works so well for them.

EDIT: I should clarify though that their schedule is almost perfectly at odds with my brother's (their dad) schedule.

No if course they don't, neither did ours (youngest still doesn't consistently at 7yo)...both our kids are ND. Key for us is division of responsibilities. One has them in the evening/night, the other takes mornings. Switch around however it fits your everyday schedule requirements. One can covee afternoons if adult naps are needed as well.

This still allows for pretty consistently getting a decent amount of sleep. If you're a single parent, then yeah it's fucked.