Well that type of instinctive love is a product of evolution. Evolution has basically programmed us in such a way as to insure the survival of our species. Our brains are chemically programmed to respond in certain ways to insure our survival. So I would say that type of love is chemical as well. Do you get physical feelings or emotions when you are around someone you love? That is a sure sign that what you are feeling is in fact a physical, material interaction of sorts.
Evolution is a scientific theory. While it explains what is physical and material, it, in and of it self, is neither.
Unless you can tell me specifically what chemical produces instinctive love and why, wouldn't this just be conjecture?