“Charity given to the needy is counted as a single charity, but when given to a relative, it is two: charity and maintaining kinship ties.”

Narrated by Aḥmad (no. 16227), at-Tirmidhī (no. 658) — this is his wording, an-Nasāʾī (no. 2582), Ibn Mājah (no. 1844), from the narration of Salmān ibn ʿĀmir al-Ḍabbī (may Allah be pleased with him).
Authenticated in Ṣaḥīḥ al-Jāmiʿ (no. 3858), and in Ṣaḥīḥ at-Targhīb wa at-Tarhīb (no. 892)

Brief Explanation of the Hadith

The Prophet (may Allah’s peace and blessings be upon him) encouraged his ummah toward various avenues of goodness — and among the greatest of them is the giving of wealth in charity. He (may Allah’s peace and blessings be upon him) then clarified that giving charity to someone who is not a relative earns a single reward: the reward of charity. However, giving charity to a relative carries a double reward: the reward of charity and the reward of maintaining the ties of kinship.
The meaning of charity also includes gifts; thus, one should show kindness to wealthy relatives through gifts, good treatment, and all that fosters affection. The intent of maintaining kinship ties is not limited to financial support, but includes every act that expresses affection and strengthens the bond.
The term 'charity' here includes both recommended (non-obligatory) charity and obligatory zakāh. It is permissible to give it to relatives, provided they are not among those whom one is legally obligated to support — such as parents (and those above them, like grandparents), children (and their descendants, like grandchildren), and anyone whose maintenance is a religious duty. However, among eligible relatives, those closest in kinship and most in need are to be given priority.
The ḥadīth indicates that giving charity to a relative is generally more virtuous than giving it to a non-relative. However, this is not absolute, for it is not necessarily the case that charity to a relative is always better than charity to a non-relative. As it is possible that the distant needy person may be in greater need of charity and benefit from it more, while the relative may be in the opposite condition.