Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.092.

The kin are considered the most deserving people for the sadaqah gift because of the common blood relationship. When a man is in need and some of his relatives are rich, naturally he looks to them for help because they are of one family. Also, it is natural for a man to feel more sympathy and pain with his hard-pressed and needy relatives than with strangers. He is humiliated by their degradation and elevated by their honour. Therefore, any well-to-do person who cuts off his kin from assistance and lives in luxury while his relatives are in a state of misery is devoid of natural feeling or lacks belief and is far away from goodness or piety. On the other hand, for one who maintains close links with his kin, his sustenance is assured and his relationship is of beneficence to his kin.