Marriage is a more specialized union that could work in conjunction with a familymaking union, but which should be distinct from it. There needs to be a way to define a /singular/ person who, when representing the other party of the marriage, has precedence over all others in a family.

A group who wish to practice polygamory but don't wish to define such precedent could choose not to split into married pairs. It is important to preserve the option to do so, however.