The short answer is no, there is no such law. Children are allowed to share rooms; the courts do not expect that all parents can afford homes large enough to allow their children to each have their own rooms.

However, if there is a custody dispute at issue, then whether the child has a room may be an issue that the court would look at. In fact, one should expect that the court will consider ALL factors having to do with the child's welfare in making its final determination. This includes the size of the home and where the child will sleep, and her level of safety and privacy in that space. To give you an example, if one parent has room enough for each child to have their own room and the other parent's home is so small that the child has to share with three other siblings, then of course that situation would favor the parent with the larger home with respect to that single issue. As another example, if a teen girl is sharing a room with an adult male, you can be sure the court will order that it be stopped immediately or possibly even remove the child from the home entirely.

If social services is involved, then the child's welfare is the main concern. A child having her own room is not the issue so much as whether the home as a whole is safe and comfortable, with sufficient space and privacy.