Storge:

"Storge Love

Have you ever seen a newborn animal? Weak, and clumsy. Literally dependent on the protection of the mother those first few crucial hours. Have you ever seen a new born baby? Again, weak, defenseless, totally dependent on the mother for survival and wellbeing. Maternal Bonds are made in those first few hours. The touching, caressing, holding, kissing of the newborn infant. Mother bonds to child, child bonds to mother. The child associates mother with safety and welfare. The mother associates the baby as one to be protected, nurtured, cared for, and loved. That is Storge Love.

Storge Love is an instinctual love. No one has to tell a new mother that she need protect and nurture her new born infant. It is automatic. Unlike Philios Love, Storge begins to "love" for the sake of loving. It is not as conditional as Philios love. A new mother loves her child simply because he or she is her child. But, Storge is self seeking to a degree. There are rewards involved in expressing and giving Storge Love, and mother and father soon learn them. Child, too, soon learns that if I do this, or do that..then I will be showered with more attention. Mom and dad soon learn that if they do something, or act a certain way, or give something to child, they too are rewarded.

http://members.tripod.com/~ALM4Ever/storge.html

Here's another great article: http://cla.calpoly.edu/~bmori/syll/311syll/Lovetypes.html