Sleeping arrangements for two teen daughters and preteen son at non-custodial parents home?

Any sleeping arrangements to be enforceable has to be in the Divorce decree.

Child and Family Services or Child Protective Services may have requirements but usually they are regarding cleanliness and actual beds not how many are in a room. If you want something that is specific then you need to request it be placed in the court order.

There are no laws about it. The rule is reasonableness under the circumstances. It is not supposed to work to penalize poor people with small houses. The genders should have the ability to dress, bathe and toilet separately. You didn't say the age of the boy. That matters. Are they curious? Were they raised together? How much room is available in the house? How many beds? Is there a couch? When I was growing up we made palates on the floor all the time. That meant piling blankets or sleeping bags on the floor topped with a sheet some pillows and a cover blanket--usually in front of the TV in the living room. It was fun for us. Between beds and the floor and couches there was always room. I am not sure people think about that these days with some of the questions I see.

Laws do not set rules or ages for living arrangements. Parents good judgment and common sense control. And then the courts review and make orders in trials.