Need sleep help pretty please :(

hopeful34

DD is STTN &  i have to wake her at 6am to go to daycare. DS sleeps until 4am & he's very hard to get down at that point. I give binky, rub his back but as soon as i leave the room the crying starts up again. If i leave him he still won't go back down. As a last resort i bring him to bed with us but this is usually after an hour. He has to get more sleep before daycare because they like to keep the same nap schedule every day.

Some info on their schedule:

 In the morning they go down around 8:30ish and sleep for 1hr (we wake them usually to keep on schedule). The next nap is around 1:30 to 3 or 3:30.

Bed time starts around 6:30 and they are in bed by 7:15. They both fall asleep on their own within 30 mins with no help. Even if he goes to bed later he wakes up at 4am.

I have no idea how to get him to sleep longer. This has been on going no matter how we change up the schedule. We don't feed him either at 4am. He hasn't gotten fed at night since like 4-5 mos. They are both a good size as well.

Help please. I need some idea's. I work f/t and getting up at 4 sucks. If he would go back it wouldn't be a big deal but he won't most of the time or if he does it's only for 30 more mins or so.

Thanks!