Asterism is very strong on the importance of oathbinding and family stability, and discourages premarital sex - which is not to say that people don't do it, just that they conceal it more. Many respectable young Silver-class Asterists, though, are naive and innocent about sex.are more open and more relaxed about sexuality than the more urban, more educated Asterists.
Reliable contraception, in the form of bone charms implanted under the skin, exists for both men and women, though women are the predominant users of it (not least because the male version is implanted in the testicles, a somewhat painful procedure). The charms are not cheap, and must be implanted and activated by at least a mage-minor in lifemagic. They are relatively specialised to make, also, and Hope at Merrybourne, despite a good education and mage-minor standing in lifemagic, had to buy one rather than making her own.
The oathbond ceremony, by creating a powerful mindmagic bond between a couple, tends to reduce the incidence of extramarital affairs, though they do occur. In the Gold Class especially, where oathbonds are often based on political alliance, it's tacitly understood that both partners may also have lovers. There is a lifemagic test, equivalent to a DNA test, for paternity, routinely performed by Gold-class people at the birth of a child, which faces people with a dilemma sometimes: do they conceal the birth of a child whose father is not the oathmate of the mother, and pass the child off to country relatives of the father or mother to raise, or do they, in effect, adopt the child into the mother's oathmate's family? The decision is a complex one and is based on a number of circumstances, including the acceptance of the love affair by the oathmate, the need for an heir, whether the mother is of higher rank (in which case the child will be part of her family in any case)...
Among Silvers (apart from those in the highest ranks, who tend to imitate the Golds both in arranging marriages and also in allowing lovers), faithfulness to one's oathmate is taken much more seriously. However, the younger generation, who are often away from their families for education in their young adulthood, and who often encounter the more relaxed morality of Earthists who are receiving the same education, are beginning to have more premarital experiences than was the case in earlier generations, where mating was strictly supervised by the families. This can lead to intergenerational clashes.
Earthists consider that openly living with one's promised oathmate is acceptable, though doing so with someone without any intent of oathbinding would be viewed somewhat askance. Asterists consider this racy.
The newspapers owned by the Tried and True Party and aimed at the lower end of the Silver Class have an especially prurient brand of Silver morality, professing to be shocked, for example, at gnomish polygamy. Scandal is their stock-in-trade, and although the newspaper owners usually manage to suppress scandal about members of their own cliques, they encourage it about their political rivals.
Sex manuals are in limited, but growing, circulation (see books). Pornography and prostitution, while legal, are marginalised and openly available only in certain areas, which are not considered respectable places to go. In higher-class areas, pornography is kept out of sight in bookshops, and high-class prostitutes are very discreet about their activities to avoid attracting the wrath of moral campaigners, or even the law.
The Code of Willing forbids regulation of the private activities of consenting adults, but the wording allows for regulation of anything that crosses the line into "public", and this is considered to include advertising or openly displaying pornography or prostitution. Basically, if anyone who is simply walking down the street, with no intent to see such things, might see them, they're no longer "private", and may be regulated by the law. Likewise if a legal minor might see or gain access to them.
There are firm views among both Asterists and Earthists that children (who have not yet reached puberty and had their childhood's end rites) should not be sexually involved, although in a crowded Earthist peasant dwelling, children will be exposed to adult sexuality. Betweeners, those who are no longer children but have not had their adulthood rites, are allowed some sexual experimentation and given some sexual instruction by Earthists, but not by most Asterists. Sexual involvement of an adult with a betweener is accepted by many Earthists but condemned by Asterists, and subject to social and legal penalty, though it does, of course, occur.
Homosexuality, bisexuality and genderqueerness are known phenomena with limited social acceptance. Since the private activities of adults are legally unregulated, as long as people keep to themselves they are tolerated, though not celebrated. However, one can register an oathbond with a member of the same gender, since the oathbond ceremony is not only for couples, and no questions will usually be asked (certainly not by the clerks, who will register any relationship you like if you submit the proper form).
The third faces of the divine in Asterism are associated with ambiguous gender (the Maker), bisexuality, homosexuality and non-binary gender (the Changer) and genderlessness/asexuality (the Ender), and each has a quiet cult and at least oneassociated with it. Their symbols are used as subtle means of recognition. There are definitely prejudices against these phenomena, which vary in strength from time to time, place to place, class to class and individual to individual, and non-heterosexual oathbonding is more likely than not to draw parental rejection among Asterists.
Among Earthists, this is even more true, and non-heterosexual couples need to keep their heads down and remain inoffensive in all other ways in order to avoid social sanction and/or violence. While, theoretically, such violence is illegal, in practice most rural wardens won't try very hard to identify or arrest the culprits.
Among dwarves and gnomes, non-heterosexual oathbinding is not practiced, and such couples must keep their relationships totally secret to avoid rejection by their societies. Sex between dwarves and gnomes (who are interfertile) is also forbidden, but does occur, with the resulting children typically being banished along with the gnome parent (at one time, they would have been killed).
Gnomes, but not dwarves, are permitted to be polygamous, since there are fewer male gnomes because of higher mortality rates in their dangerous occupations. Polygamous gnome oathbonds are always with the consent of all parties involved. Modern, emancipated gnomes tend to look on polygamy as old-fashioned and part of the bad old days of dwarven oppression, though a few still practice it.