How do children go to bed hours later than usual bedtime and somehow still wake up at 6.30am to…

How do children go to bed hours later than usual bedtime and somehow still wake up at 6.30am to 7.30am. I'm shattered. And apparently Zaid's deciding to drop his morning nap. Used to be 1 hour + and last few days it's barely been 30 minutes and yd he went completely without! My pregnant self can't handle this lack of sleep!