Help 😭

My son will not sleep past 4am!! I’ve tried going to bed later, I’ve tried going to bed earlier (someone said if they are over tired means worse sleep?)...It doesn’t matter if he has had a lot of naps during the day or barely any. He will without fail wake up at 4am. Is there anything I can do? 😭😭 he wakes up happy, and ready to play. He won’t go back to sleep until about 6-6:30. Help 😴