This kind of thing has been around longer than you know. While touring the city of Rome, I passed over a cemetary area for the Leigon. Off to one side, but still a part of the main cemetary was a smaller section, with smaller stones. At first, I thought it must be for children attached to the roman army for purposes of family or ground support. When I started examining the stones closer, I realized I was looking at the final resting place of a decurion's dog. The whole smaller section was reserved for the pets of officers and enlisted men. The markers contained the pet's name, species, a short message, and the owner's name. Often, the owner was buried adjacent to the pet in the next section over.
We've associated ourselves with animals on a very personal level for longer than our species has had writing. What's so suprising that people consider pets as vital parts of the family?