Is it permissible to kiss the maternal aunt's husband or not?

The mother's maternal uncle (khal al-umm) is considered a mahram (unmarriageable kin), and he is in the position of a maternal uncle because he is the grandmother's brother. It is permissible for mahrams to kiss one another if there is no fear of fitnah (temptation) and no apprehension of lust. The kissing should be on the forehead and the head, not on the mouth, as narrated from Imam Ahmad. Examples of this have been reported from the Salaf, such as Abu Bakr kissing his daughter Aishah, and the Prophet (peace be upon him) kissing his daughter Fatimah.