Praise be to Allaah.
You have to look for the reason, for it is not normal for something like this to happen without a reason, but that reason may be unknown to you. If you did not do anything deliberate to upset him, then do not feel responsible for what has happened and for his cutting off ties with you. You have to be patient and treat him well even if he mistreats you. Perhaps he will come back to you when he sees your good attitude.
In many cases, this kind of rigid and harsh-hearted attitude is temporary and does not last for long; it may stem from a particular incident which made the person angry, but when his anger has calmed down and some time has passed, things go back to the way they were, or close enough. Perhaps some extreme circumstances coincided with a bad attitude, hatred or an inclination to bear grudges, which resulted in a long-term estrangement. In this case all parties concerned should be given time to calm down gradually, so that the bad feelings may be reduced; at the same time, the person who has cut off ties of kinship should be reminded of the rights of his relatives, what Allaah and His Messenger say on this matter, and the stern warning issued to those who cut off ties of kinship. If any of the parties involved have been wronged, things must be put right as quickly as possible, and there is nothing wrong with trying to heal the wounded pride of the party that has been wronged, by apologizing or getting together for the purpose of reconciliation, etc., as Allaah says (interpretation of the meaning):
“and adjust all matters of difference among you” [al-Anfaal 8:1].
We hope that the one who undertakes to reconcile between them will earn the reward mentioned in the aayah (interpretation of the meaning);
“There is no good in most of their secret talks save (in) him who orders Sadaqah (charity in Allaah’s Cause), or Ma‘roof (Islamic Monotheism and all the good and righteous deeds which Allaah has ordained), or conciliation between mankind; and he who does this, seeking the good Pleasure of Allaah, We shall give him a great reward” [al-Nisaa’ 4:114]
Sometimes it may be better to avoid getting involved in looking for a reconciliation until things have calmed down and people are more likely to agree to open the issue and listen to those who want to reconcile between them and accept their suggestions.
We ask Allaah for guidance.