I tend to agree with with DarknessIsMyFriend. It is an evolutionary trait to push us to breed and keep our descendants, as we are pushed to eat and drink. Between a man a woman "love" pushes us to have sex. Between parents and children "love" pushes us to keep the genes. That is why I think there is a natural love from parents to kids but not the opposite. I think the word love is an invention for something doesn't really exist. Having said that, this idea is not welcomed and almost all people like to think of love as something divine.