In past societies, marriage was intended to insure the genetic code of a man’s children and the financial support of those children’s mothers (or a man’s daughters upon adulthood). Marriages were arranged, much in the manner that animal breeders will pay for their prize dog or horse to mate with a genetically-advantageous partner, with financial and material arrangements as detailed as any modern limited-liability business partnership.

The legal side of what we call marriage should be acceptably covered by interpersonal documents of mutual support and exclusivity, which should be limited neither by number nor by gender (and arguably, not even by consanguinity, as it is often that the nonmarried elderly live with siblings and/or nonmarried children in a pooled-income household, or that adults financially support distant adult children or elderly parents).

Some would argue that this sort of arrangement does not naturally include conditions for the addition of partners to the household, departure of partners therefrom, and those issues relevant to the birth and rearing of children or the care and housing of those partners who become incapacitated. These are all issues that can and should be enumerated in the legal contract.