I live in place called Trinidad & Tobago, most of tu probably have never heard of it.
Here is a copy for where I live of some of that law:
A common-law o cohabitational relationship arises when there are two persons of the opposite sex, who not being married to each other, are living o have lived together as husband and wife. In Trinidad and Tobago, the parties to a common-law relationship have rights under the Cohabitational Relationships Act and the Distribution of Estates Act.
Most places it is considered "Statutory Rape" if a person of legal age has sexual relations with a minor, but there are some religious and cultural exceptions.