Undoubtedly severing ties of kinship is a major sin. The many texts of the Qur’an and Sunnah that enjoin upholding ties of kinship highlight the great importance of this matter in our religion. One of the greatest aims of sharee‘ah is to bring people together and maintain the ties of brotherhood and kinship among them. 

Allah, may He be glorified and exalted, says (interpretation of the meaning):

“Those who join that which Allah has commanded to be joined (i.e. they are good to their relatives and do not sever the bond of kinship), fear their Lord, and dread the terrible reckoning (i.e. abstain from all kinds of sins and evil deeds which Allah has forbidden and perform all kinds of good deeds which Allah has ordained)”

[ar-Ra‘d 13:21].

 Among the reports of the Prophet’s Sunnah which give a stern warning against severing ties of kinship is the following: 

it was narrated that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said:

“Allaah created the universe, and when He had finished, kinship (al-rahm) stood up and said, ‘This is the standing up of one who seeks Your protection from being cut off.’ Allah said, ‘Yes, would it please you if I were to take care of those who take care of you and cut off those who cut you off?’ It said, ‘Of course.’ Allah said, ‘Then your prayer is granted.’” 

Then the Messenger of Allah (blessings and peace of Allah be upon him) said: “Recite, if you wish: ‘Would you then, if you were given the authority, do mischief in the land, and sever your ties of kinship? Such are they whom Allaah has cursed, so that He has made them deaf and blinded their sight. Do they not then think deeply in the Qur’aan, or are their hearts locked up (from understanding it)?’ [Muhammad 47:22-24].” 

Narrated by al-Bukhaari, 5987; Muslim, 2554 

If people were to ponder what causes the severing of family ties amongst them, they would find the cause is disputes some materialistic issues which will not avail for anything before Allah on the Day of Resurrection; or it may be because of what the Shaytaan stirs up amongst them, leading to enmity and resentment amongst them because of insignificant reasons that are not worth paying any attention to in the first place. 

That happens despite the fact that Islam enjoins upholding ties of kinship even if there are considerable reasons for cutting ties, and it encourages the believers to overlook mistakes and to adopt a forgiving and tolerant attitude, not to seek out mistakes and nurture resentment, grudges and envy. 

It was narrated from Abu Hurayrah (may Allah be pleased with him) that a man said: O Messenger of Allah, I have relatives with whom I try to keep in touch, but they cut me off. I treat them well, but they abuse me. I am patient and kind towards them, but they insult me. He said: “If you are as you say, then it is as if you are putting hot ashes in their mouths. Allah will continue to support you as long as you continue to do that.”

Narrated by Muslim, 2558 

An-Nawawi said in Sharh Muslim (16/115):

Ignorance here refers to bad speech. What this hadeeth means is that it will be like feeding them hot ashes. This is a metaphor for the pain they will feel, like the pain of one who eats hot ashes. There will be no sin on this doer of good, rather they will be sinning greatly for cutting him off and causing him harm. 

And it was said that what is meant is that by treating them kindly you will make them feel ashamed of themselves because of how kindly you treat them and how badly they have treated you. And Allah knows best. End quote. 

The Prophet (blessings and peace of Allah be upon him) said:

“The upholder of kinship ties is not the one who is kind to them if they are kind to him, rather the upholder of kinship ties is the one who, if his relatives cut him off, he upholds the ties of kinship with them.”

Narrated by al-Bukhaari, 5991. 

This is the conduct and attitude enjoined by Islam. No one should hesitate to denounce one who cuts off ties with his sister or his mother. It is not permissible for you to go along with your father in cutting off ties with his sister; rather you have to uphold ties with her and treat her kindly, and try to reconcile between her and your father, doing all that you can to achieve that. 

Please see also the answers to questions no. 4631, 7571 and 75411 

And Allah knows best.