Is it lawful for boys to kiss their stepmother?
What is her relationship to them? Is she considered as their mother, paternal, or maternal aunt? What is the wife's father considered to be for his son in law?
It is enough for boys to shake hands with their stepmother. The same applies to the father in law with regard to his daughter in law, and the daughters of his son in law as he is their grandfather (if they are his daughter's) thus, he may greet and shake hands with them. There is no harm in a man kissing his mother in law when arriving from a journey or the like, but it is better not to be on the mouth. It is preferable for him to kiss her on the forehead, nose or cheeks. Moreover, there is no harm if a man calls his mother in law aunt, or his father in law uncle. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.