21MO co-sleeper clearly tired during the day. How to get him better sleep?

[KLM99]

I have been cosleeping with my 21mo since he was born and he's never been a great sleeper.  Lately he's been tired and cranky in the morning when he wakes up, hasn't been napping well and then has been losing it in the evening.  I just don't think he's getting good sleep.  He sleeps from about 8pm-1am and then wakes up to nurse a few times between 1am and 4am.  Then he sleeps until about 7am, but somewhat restlessly. 

Any ideas for getting him to sleep better during those early morning hours?  It's like he can't settle back down after he wakes up the first time.