What is the ruling on a sister kissing her brothers in public places?

Praise be to Allah.

Firstly:

There is nothing wrong with a man kissing his mahram – his paternal aunt, maternal aunt, mother, grandmother or sister – and that should be on the head, on the nose or on the cheek, according to what is customary among the people. The majority of scholars regarded it as makruh (disapproved) to kiss anyone on the mouth except the husband.

Similarly, there is nothing wrong with his mahram – such as his sister, paternal aunt or maternal aunt – kissing him on his head or cheek. But that should not be a habit that they do regularly; rather it should only be when he returns from a journey and the like. As for them taking kissing as a regular habit, that is not appropriate according to Islamic teachings.

It is also stipulated that both parties should be safe from fitnah (temptation).

Ibn Mansur asked Imam Ahmad: Can a man kiss his mahrams? He said: If he has returned from a journey and does not fear any fitnah from that, and he quoted the hadith of Khalid ibn al-Walid, according to which the Prophet (blessings and peace of Allah be upon him) returned from a military campaign and kissed Fatimah (may Allah be pleased with her).”(Al-Furu‘  8/191).

Secondly:

With regard to kissing them in public places in front of other people, that is not appropriate, because it is improper and undignified. The scholars (may Allah have mercy on them) stated that it is makruh (disliked) for a husband to kiss his wife in front of people, because it is contrary to the decency and dignity that the Muslim should observe.

If that is in a public place where the people do not know that she is his sister or one of his mahrams, then it is even more disliked, because it opens the door to people thinking ill of them.

There may be a concession allowing that if it is in particular circumstances and there are other signs which indicate that this is a man kissing his sister or one of his mahrams, such as if that happens at an airport or port when people are bidding farewell to a traveller or welcoming one who has returned, and if the man or woman are old.

Or if they both appear to be people of modesty, good manners and religious commitment, in which case the kiss would not lead the onlooker to think ill of them and it would not offend public decency, so it is not far-fetched to suggest that a concession may be allowed in that case.

And Allah knows best.