Does the humane society have right to kill a healthy 3yr old family pet dog?

No, the humane society does not have the right to kill a healthy 3-year-old family pet dog. The humane society is an organization dedicated to the welfare of animals, and their policies are designed to protect animals from harm. Euthanasia is only considered as a last resort, when an animal is suffering from a serious illness or injury and there is no other option to alleviate their pain. In the case of a healthy 3-year-old dog, there is no reason for the humane society to euthanize the animal.