Within Thedas, there are several different views in regards to sexuality. Among all groups is the viewpoint that marriage is not a romantic affair, but a duty to one’s family.
Viewpoints
Alienage Elves
The elders of an alienage arrange marriages for the elves living within it, typically to an elf from a different alienage. This is to keep the ties between alienages strong while preventing interbreeding in the small and isolated communities. After the marriage is arranged, dowries are exchanged. Sometimes the bride will move to the groom’s alienage and other times it’s the opposite; it depends on who is willing to pay more to keep their child. Without a sufficiently large dowry, an elf has very poor prospects.
The Chantry
According to the Chant of Light, Andraste had a spiritual marriage with the Maker. For them, marriage is a matter of tradition and practicality, and a holy bond between man and woman. Love is not necessary, but love within marriage is the ideal. Other than that, the Chantry has few regulations regarding sexuality.
The Chantry does not have divorce, but a marriage can be annulled.
Dwarves of Orzammar
The dwarves of Orzammar have one of the most sensuous cultures in Thedas. Polygamy is legal, as are brothels.
Grey Wardens
Although Grey Wardens are not forbidden to marry, tradition goes against it. Usually someone joins the Grey Wardens for life.
Mages
Mages tend to be more promiscuous than the average population. They are free to act as they desire and not considered bound by normal social mores as they are not considered part of normal society. They are not encouraged to marry or have children for practical reasons.
Orlais
Aristocrats in Orlais like to outdo each other when it comes to showing off their extravagant tastes, sexual or otherwise. The peasantry is much less tolerant of such things, at least in private. According to The Stolen Throne, the ruler of Ferelden during the Orlaisian occupation, Meghren, reputedly had sexual relations with his cousin Florian, the Emperor. There was perhaps some scandal involved that led to Meghren being "banished" from Orlais to be King of Ferelden, but this may be more a result of the fact that Florian was Meghren's cousin rather than the nature of the relationship itself.
Qunari
The attitudes of the qunari towards sex and marriage are unknown. Other races might be surprised to learn that the qunari have relationships of any kind.
Homosexuality
The majority of Fereldans consider same-sex relations odd, but not immoral, while Orlesians consider it a quirk of character.
Interracial
The children of elves and humans are always human. As the elves are a dying race, there is a great deal of pressure for each member to produce children. Relationships with humans are considered traitorous and anyone who has a child with a human may be kicked out of the community.
Dwarves have difficulty reproducing and many dwarves consider humans and elves lesser races. For this reason, they are also against interracial relations. Humans and dwarves can produce half-dwarves, but this is very rare.