Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
- The Prophet Muhammad (peace be upon him) used to kiss Al-Hasan and Al-Hussain.
- Only the parents can kiss their daughters on the mouth as no desire can be assumed behind such an act.
- The age is a factor that daughters should not be over a year or two old.
Answering your question, Sheikh Kifah Mustapha, the Imam and Director of The Prayer Center of Orland Park and representative for Dar El Fatwa of Lebanon in the US, states:
We have references from the Sunnah that the Prophet Muhammad (peace be upon him) used to kiss Al-Hasan and Al-Hussain (may Allah be pleased with them).
Abu Hurairah reported that Al-Aqra ibn Habis saw the Prophet kissing Al-Hasan. He said: I have ten children, but I have never kissed any one of them, whereupon the Prophet said: “He who does not show mercy (towards his children), no mercy would be shown to him.” (Muslim)
There is also one narration that the prophet (peace be upon him) kissed once Al-Hasan on his lips and said that no lips shall touch Hell that were touched by the prophet’s lips. (Imam Ahmad)
This was only a one time incident, and the most practice was that kids are kissed on the cheek, head, hand, feet etc. but not the mouth usually.
And for that, I am not in favor for kissing daughters on their lips at all and the way I see the hadith mentioned above that it was a special matter to the Prophet only for the very reason mentioned that Al-Hasan lips shall not touch fire.
Now if someone did it, I can think of some regulations like only the parents, as no desire can be assumed behind such an act and that the age is also a factor that kids should not be over a year or two old.
Almighty Allah knows best.