How does that make it not a kind of marriage? Just because our particular cultural tradition of marriage is "till death do us part", that doesn't mean it's an inherent part of the concept. In some cultures, for example, marriage is basically the act of announcing to the social group who the father of a child is, which further serves to obligate the father to provide some care for the child and its mother. The idea of a "marriage" existing beyond the time the child leaves on his own would seem bizarre. --LDC