Is it permissible for an adolescent boy to kiss his younger sister's foot if she asks him to do so in order to answer her question, knowing her extreme keenness on caring for her feet?

The sister must be admonished for her request, and it should not be granted, especially if its reason is self-admiration and pride in her feet. It must be clarified that this is unacceptable, particularly from a younger sister to an older brother. The Islamic etiquette is for the younger to show respect to the elder, and for the elder to show mercy to the younger, as the Prophet, peace and blessings be upon him, said: "He is not of us who does not have mercy on our young and does not respect our elders."