I feel for you. As I have one who only sleeps 30mins. maximum 40. But things are getting better.

I do not take him even if he cries. He has to stay in his playpen until the other kids are up. I would let him stay in his playpen and would not pick him up. This way he learned how to put himself back to sleep or may be bordem made him sleep. He cried of course but I know he is safe, clean and fed so he has no reason to cry. As Judy said already "It will get better when he realizes that no amount of crying is gonna get him up and he will stop."

And also during the day, I sometimes put him on his playpen and put some toys with him so he will get used to his playpen.

Good luck just be persistant.
Cocoon