Is what an unmarried man spends from his salary on his family (for food, drink, and clothing) or gives to his sisters or uses to buy household food considered charity, and is that sufficient for the intention of both charity and assistance?

Spending on family and relatives is considered charity and is better than giving charity to others because it combines both charity (ṣadaqah) and maintaining kin ties (ṣilat ar-raḥim), which results in a greater reward. This includes both obligatory and voluntary spending on family and relatives, regardless of whether the relative is someone whose maintenance is obligatory or not.