I heard the following story from a learned person. Some rustic people (as usual known for their sturdy and rough life style) were visiting beloved Prophet (PBUH). After prayers beloved Prophet (PBUH) kissed either Hazrat Hasan (RA) or Hazrat Hussain (RA) - whoever was present. The visitors were shocked. How can you treat the would be man in such a soft manner, they asked? Beloved Prophet (PBUH) siad, "What can I do if your hearts have become non-loving". This is basically the gist of the event. The details will certainly be different.