Since when does "couple" mean three

Throughout the article, "Three-Way Marriage Ignites Uproar in Brazil," I kept asking myself, "How does couple now mean 'three'?"

Apparently, two women and one man recently "married" in Brazil, and defenders say the "couple" has the right to do so.  

The article focuses on one thing that the three individuals share -- their bank account -- as if shared finances are the stuff of which marriages are made.

And then there's this comment:

International television network Globo TV claims that the couple has been married for three months but just recently their union was made public.

Jurist Nathaniel Santos Batista Junior said the union was kept hushed to protect the rights of the couple in case they decided to separate or if one of the partners died, said a report from Globo.

Right.

How is this marriage?  

If it's all about some shared money and it requires secrecy in case someone changes his or her or her mind or dies, and it involves three people, then what resemblance to marriage does it really bear?  Why is marriage now seen as a continually evolving, formless blob that caters to our every whim, fantasy and desire?

But, on the other hand, if marriage has an objective form, if in a way, we serve marriage and the purposes inherent to it, then the way we view this Sacrament and vocation will be very different.