The "Housing Act 1985" states that a dwelling is considered as "overcrowded" if two persons of different sexes, who are not married, have to share a same room for sleeping purposes. However, children under the age of 10 can share a room regardless of their sex.
Once the children have reached the age of 10, they have to be given their own rooms if they are of the opposite sex. But in case the children are of the same sex, sharing a room up to 20 years of age is permitted by the law. After 20, every person is treated as an adult and must have an individual room.