All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The Sharee’ah did not define in precise terms the amount or kinds of keeping ties with kinship, but rather it left the matter to the customs and traditions of people like many matters which the Sharee’ah did not limit them to any specific thing, so we refer to what is customary among people in this regard.
Ibn Taymiyyah said: “We refer in the matters which are defined in the Sharee’ah or language to the Sharee’ah and language, and we refer to what is customary among people in the matters which are not defined in the Sharee’ah or language.”
In many societies now, it is known that a phone call is a kind of keeping ties, so you would not be severing the ties if you make a phone call to your brother.
However, you may ask your brother about his wife, his children and their studies and similar matters that could be a subject of discussion between both of you. Also, you may seek his advice about some personal matters if you know that he can advise you.
Allaah Knows best.