Answered by Sayyidi Habib Umar bin Hafiz (may Allah protect him and benefit us by him).
How can we improve our relations with our relatives?
You can do this by sincerely wanting the best for them and using wisdom and gentleness in your dealings with them.
Repeat the following verses:
هُوَ الَّذِيَ أَيَّدَكَ بِنَصْرِهِ وَبِالْمُؤْمِنِينَ وَأَلَّفَ بَيْنَ قُلُوبِهِمْ
لَوْ أَنفَقْتَ مَا فِي الأَرْضِ جَمِيعاً مَّا أَلَّفَتْ بَيْنَ قُلُوبِهِمْ وَلَـكِنَّ اللَّهَ أَلَّفَ بَيْنَهُمْ إِنَّهُ عَزِيزٌ حَكِيمٌ
It is He Who has strengthened you with His aid and with the believers; He has united their hearts. Had you spent all that is on the earth, you could not have united their hearts, but Allah has united them. Truly He is Mighty and Wise. (Al-Anfal, 8:62-3)
You can also repeat the last two verses of Surat al-Tawbah (9:128-9). Repeating these two verses for 41 days with the intention of bringing their hearts together is a means of rectification.
The following Prophetic supplication can also be recited to bring harmony and remove hatred:
اللَّهُمَّ اقْسِمْ لَنَا مِنْ خَشْيَتِكَ مَا تَحُولُ بِهِ بَيْنَنَا وَبَيْنَ مَعَاصِيكَ
وَمِنْ طَاعَتِكَ مَا تُبَلِّغُنَا بِهِ جَنَّتَكَ
وَمِنَ الْيَقِينِ مَا تُهَوِّنُ بِهِ عَلَيْنَا مَصَائِبَ الدُّنْيَا
‘O Allah, apportion to us fear of You which prevents us from disobeying You; enable us to perform acts of obedience which cause us to reach Your Garden of Paradise and bless us with certainty which softens for us the calamities of this worldly life.’