To what extent can messages be shared on WhatsApp? I mean between brothers and sisters, and their husbands and the wives of brothers, on a daily basis; this includes joking, video messages, and sometimes un-Islamic content; is this considered part of upholding the ties of kinship?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.

The answer to this question requires some details; if these messages are shared in a group in such a way that all members of the group get to see them, then there is no harm in that provided that they do not include any Sharia violations such as mockery, lying, and the like. There is no doubt that if these messages are in accordance with the Sharia, then they are considered to be part of upholding the ties of kinship.

However, if these messages are shared in a private chat between a male and a female who are non-Mahram (marriageable) to each other, then it is prohibited because it may lead to Fitnah (temptation) and may open the door for Satan to them into committing Sharia violations. Allah, The Exalted, says (what means): {O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - indeed, he enjoins immorality and wrongdoing. And if not for the favor of Allah upon you and His mercy, not one of you would have been pure, ever, but Allah purifies whom He wills, and Allah is Hearing and Knowing.} [Quran 24:21]

Allah knows best.