At what age do children of opposite sex have to stop sharing bedrooms

Kids these days tend to grow up fast mentally, so I'd say about six.

There is no "law" in some poorer households families of 3 or 4 kids may have to share one or two bedrooms, it is a fact of life in today's economy.

If Children services are investigating, they will have guidelines often based on the opinion of the social worker doing the investigation.

How old are the kids, are they full brother and sister, or step

When you say "have to stop" sharing a bedroom, do you mean legally "have to stop" or what is appropriate?