Marriage

Marriage is a peaceful method by which two nobles can unite their Houses and pool their wealth and power.

Codex
"Marriage is one of the most important social institutions in post-Collapse culture, for two reasons.

First, because legitimate power can only be transferred through inheritance, marriage is one of the key ways an ambitious house or individual can gain power.

Secondly, acting in bad faith towards one's kin is universally considered dishonorable. Marrying into a family is a good way to discourage them from seeing you as a military target. In general, a crime against a family member is considered a more heinous crime. There is also an expectation that kin members will defend each other from aggression.

Because of how valuable marriage is to form alliances amongst the nobility (and keep the peace), dissolving a marriage through divorce is widely frowned upon.

When two members from different houses are married, the younger partner becomes a member of the older partner's house.

The spouse of a ruler or leader also has rights by virtue of their position. If an acting head must take the reins temporarily, they are usually chosen. They are also widely expected to occupy one of the council member positions in the house."