فَهَلْ عَسَيْتُمْ إِن تَوَلَّيْتُمْ أَن تُفْسِدُوا۟ فِى ٱلْأَرْضِ وَتُقَطِّعُوٓا۟ أَرْحَامَكُمْ ﴿٢٢﴾
Would ye then, if ye were given the command, work corruption in the land and sever your ties of kinship?
Is cutting off family ties haram?
Haram Family & relations Quran · 3
Short answer
Yes. The Quran warns that those who cut what Allah ordered to be joined are cursed (47:22-23, 13:25). Keeping ties includes visiting, greeting, helping and forgiving relatives, even when they are unkind.
Evidence
Quran
أُو۟لَٰٓئِكَ ٱلَّذِينَ لَعَنَهُمُ ٱللَّهُ فَأَصَمَّهُمْ وَأَعْمَىٰٓ أَبْصَٰرَهُمْ ﴿٢٣﴾
Such are they whom Allah curseth so that He deafeneth them and maketh blind their eyes.
وَٱلَّذِينَ يَنقُضُونَ عَهْدَ ٱللَّهِ مِنۢ بَعْدِ مِيثَٰقِهِۦ وَيَقْطَعُونَ مَآ أَمَرَ ٱللَّهُ بِهِۦٓ أَن يُوصَلَ وَيُفْسِدُونَ فِى ٱلْأَرْضِ ۙ أُو۟لَٰٓئِكَ لَهُمُ ٱللَّعْنَةُ وَلَهُمْ سُوٓءُ ٱلدَّارِ ﴿٢٥﴾
And those who break the covenant of Allah after ratifying it, and sever that which Allah hath commanded should be joined, and make mischief in the earth: theirs is the curse and theirs the ill abode.
This is general information, not a fatwa. For your own situation, ask a qualified scholar.