The fact that companion animals can and frequently do play a much larger role in people's lives than the legal system ever gives them credit for is certainly nothing new at this point to those of us who toil daily in animal law. Perhaps someday (I should live so long) courts will be willing to take judicial notice of the fact that humans develop deep, loving bonds with companions that differ - at most - by degree, but not by kind from the sorts of strong attachments we feel with other family members.
But until then... it is definitely helpful to at least be able to go to court armed with brand-new research on the subject. The October 2009 issue of Family Process apparently contains just such research. I just read about this in today's "Bites" by Doug Powell at Kansas State (thanks, Doug!) and so have not had a chance to verify this for myself yet, but apparently there are two articles on the subject by Dr. Froma Walsh (of Chicago, no less... I will try to look her up...).
According to Doug: "Media wishing to receive a PDF of this article may contact email@example.com. To view the abstract for this article, please visit http://www3.interscience.wiley.com/journal/123189842/abstract."