What is the ruling on the action of a husband who donates a portion of his family's limited income to his smoking relatives, while his own family suffers from financial hardship that prevents them from meeting their basic needs and saving anything for the future?

The basic principle is that the wife and children take precedence in spending over other relatives, based on the hadith of Jabir (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "If one of you is poor, let him start with himself. If there is extra, then for his dependents. If there is still extra, then for his relatives." If he has more than enough for their expenses, then it is permissible for him to give charity to his relatives. However, if there is nothing left over, and his wealth falls short of providing for his dependents, then it is not permissible for him to give charity and neglect his dependents, due to the saying of the Prophet (peace and blessings of Allah be upon him): "It is sufficient sin for a person to neglect those whom he is obligated to support."