How to maintain ties of kinship with kaffir family, what can you do if they constantly say kufr, and every time they say their greetings they say words of kufr in them, is it sinful if listen to them say these words and stay silent?Anytime that they call, message, speak they say these words so how can possibly keep ties?And what if grandmother is crying and sobbing and saying is going to travel all the way to meet if not repsonding to calls.Will Surah An-Nisa 140 apply?

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, sallallaahu 'alayhi wa sallam, is His slave and Messenger.

Maintaining ties with non-Muslim relatives is generally permissible, particularly if there is hope that doing so might encourage them towards Islam and incline their hearts toward it, with the potential outcome of them embracing Islam. This relation should be leveraged for this purpose. Therefore, if the grandmother reaches out to you, it is appropriate to respond to her call. The fact that her speech may contain some words of disbelief does not legally prevent responding to her. Such issues should be gently and kindly corrected if they arise.

The principle of enjoining good and forbidding evil applies to both Muslims and non-Muslims, though the approach varies. A Muslim is enjoined to do every good and shun every evil, whereas a non-Muslim is first invited to Islam. The Prophet practiced this when sending out the callers to Allah (to disbelievers). He would instruct them to impart Allah’s signs of greatness and power with wisdom and sincere admonition, underscoring the necessity of faith in Him, His oneness, and the gravity of associating partners with Him or disbelieving in Him. This constitutes enjoining good verbally. If someone can enjoin good verbally but fails to do so, he is sinful. If he is unable to do so verbally, this responsibility is waived, and he is then obligated to disapprove of it in his heart, which involves detesting what angers Allah and not condoning it.

The verse in question [Quran 4: 140] suggests the obligation to leave a place where evil exists. However, if one remains in such a place for a legitimate reason, such as to forbid it as much as he can, then he does not fall under the warning included in this verse.Ibn Taymiyyah commented on this verse, stating: “This means that one should not witness evils without need….. unlike someone who is present to disapprove of their act or has no choice in being there.”

Allah knows best.