Storge (storgē, Greek: στοργή) is fondness through familiarity (a brotherly love), especially between family members or people who have otherwise found themselves together by chance. It is described as the most natural, emotive, and widely diffused of loves: natural in that it is present without coercion; emotive because it is the result of fondness due to familiarity; and most widely diffused because it pays the least attention to those characteristics deemed "valuable" or worthy of love and, as a result, is able to transcend most discriminating factors.
Affection, for Lewis, included both Need-love and Gift-love; he considered it responsible for 9/10th of all solid and lasting human happiness.[8]
Ironically, however, affection's strength is also what makes it vulnerable. Affection has the appearance of being "built-in" or "ready made", says Lewis, and as a result people come to expect it irrespective of their behavior and its natural consequences.[9] Both in its Need and its Gift form, affection then is liable to 'go bad', and to be corrupted by such forces as jealousy, ambivalence and smothering.[10]