To Sleep or not to Sleep

Our evening routine is predictable: dinner, bedtime for the kids, and then I usually follow shortly after. However, what I've noticed is that if I make it past that 9 - 10pm siren song of my pillow, I can stay up working until 3am with ease. What's peculiar though is that I'll finally call it a day, go to bed, and find it challenging to fall asleep. I could have passed out immediately at 9:30pm, and here we are five or six hours later and my brain is just GOING.

Maybe its a sleep rhythm / cadence thing that I'm throwing off when I stay up late?

Weird stuff.