staying in bed

My son is 20 months and in a big bed, his 5 month old brother is in the crib. This was fine for the first month and now suddenly he will not stay in his bed. I am consistent and very firm, with a bedtime routine that has not changed in a year. Last night We started at 7pm and he finally fell asleep at 9pm. He is exhausted and miserable and I am at my wits end. Short of sitting on the end of the bed, which he finds quite entertaining, I dont know what else to do.
He climbs out of the crib and the playpen.
I'll try anything.....Please advise.

[Kevin Kennedy, Ph.D.]

Unfortunately, you're in a predicament for which there is no easy solution. Actually, you're probably doing the best that can be done under the circumstances. Your son is really too young to be in a bed - he should still be in a crib. Many parents find themselves moving toddlers from a crib to a bed so that the crib can be available for a sibling. But the best solution is to have more than one crib (these can then be configured - via extenders - so that a child can't climb out).