Hi Helenemjay
A few ideas. Hope they help.
Ds1 has had a lot of changes in his life recently - ds2 moving into his bedroom, new baby sister arriving. Maybe he's trying to tell you something! That doesn't make his behaviour OK - you and his two siblings need their sleep. (My ds1 is quite a lively character with a very strong will of his own to say the least, but heaven help him if he wakes us up. When Mummy is tired, she is grumpy and that means noooo treats. At all.)
Perhaps you could offer rewards, and if he stays quiet until 6.30/6.45/7.00 then he gets a treat. Once he has hit the first target, you can extend the time. If he can't tell the time, use a timer socket attached to a lamp. You set the timer, and the lamp switches itself on,
(If he wakes early and can't sleep/entertain himself, could he come into your room, perhaps on a spare matress, if he snuggles down quietly/looks at books/does a puzzle? It would be a treat for him, only on the condition that he is quiet and lets the others sleep.)
When we went through a bad patch recently, and I felt that life was out of my control, I sat down with ds1 and I wrote out a list of houserules, that absolutely must be stuck to. I found it really useful being able to talk to ds1 as we did it. When we had ten, he then helped me to put them in order of the most important first. As we did it, I was able to congratulate him on being really good at some of them, but able to chat about the two or three that he really needed to work on. I came out feeling much more in control - and I have my piece of paper to refer to when things start to go wrong. (You can draw little stick men pictures to go with the words - or ds1 could do some pictures too)
Good luck.