Fortian

• Only between people of similar status (only between citizen)
• Only between "adult" (children aren't citizen)

There is a strong expectation of producing an heir. If not able, fostering a nibling as an heir is essential. The duty of a citizen is to produce an heir first before any gains from other relationships. So it is considered more appropriate for a widow, or a parent to have multiple relationships than for an unwed or childless citizen.

Relationships between direct familial relationships (siblings, parent-child) are frowned upon but common amongst powerful families. But relationships within the same family tree are encouraged.

There are no taboos about same sex relationships or age difference between citizens (children aren't citizens). Tho it is known and becoming fashionable for a citizen and a soon-to-be citizen of the same sex to have a relationship. Publicly it is to be shown as only a mentor-mentee relationship, but in privacy, it can be otherwise.

Also, there is no power dynamics or shame in being the receiving or giving partner in the dynamic. It is considered just a matter of taste.