I think what they're talking about is creating a body of law to define custody rights and inheritance rights for people in polyamorous families. Polyamory is not as uncommon as one might think. I know people that live in this situation though none have children.

But it does happen where say, Pariah & Lor, a married couple hook up with G-man & Batwoman, another married couple, and form a household. In the course of this liason Pariah and Batwoman produce a child. In the event of a break-up, who should have the rights of paternity, G-man or Pariah (imagine picking one of those wankers for a father)? Or G-man dies intestate. How should the rich lawyers dough be distributed?

Does current law aimed at traditional couples provide equity in these situations? I think not. And what does incest have to do with polyamory anyway?