My ex-husband makes my 13 year old son sleep not only in the same room but in the same bed with my 5 year old daughter.Is there a law about that?

Who has custody ? Is this merely for a couple nights a month if he has visitation ?

Not knowing your local, in general, there are no laws, people who are poor and can not afford multiple bed rooms often have family that share beds, It was much more common many years ago, and is still common in some culture more than others.

If is is a issue and merely a visitation time, perhaps the 13 year old can take a blow up mattress with him.

So you are afraid your 13 year old son will molest his sister ? Has the 5 year old said something that makes you think the 13 year old is doing something improper

I think that given the immaturity of children, and the hormonal changes that could possibly be taking place in the thirteen year olders body, the dad is really taking a chance that something inappropriate might happen. Please tell the father not put his son and daughter in this position. A momentary lapse in judgement on their parts could lead to a lifetime of horrible consequences.

If you have raised your son and daughter properly, making them aware of inappropriate touching, this shouldn't be a problem on a short term basis. I'll assume this is done on weekend overnites. I'm also assuming that your ex-husband is living in smaller quarters due to support obligations.

Unless you have any reason to suspect that your son doesn't know the boundaries, this sounds more like a vendetta against your ex rather than a real concern.