If he gives iftaar to a rich relative, he will have the reward of one who gives iftaar to a fasting person
This hadeeth was narrated by al-Tirmidhi (807) from Zayd ibn Khaalid al-Juhani who said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever gives iftaar to one who is fasting will have a reward like his, without that detracting from the reward of the one who fasted.” Classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.
This hadeeth is general in meaning and applies to all who fast, whether they are rich or poor. It also includes relatives and others.
See Fayd al-Qadeer by al-Manaawi, commentary on hadeeth no. 8890.
Indeed, giving iftaar to a fasting person who is a relative may bring a greater reward, because by doing so you may earn the reward of giving iftaar to one who is fasting and of upholding the ties of kinship, so long as the one who is not a relative is not a poor person who cannot find any food with which to break his fast, in which case giving him iftaar will bring a greater reward because that will be meeting his needs.
By the same token, giving charity to a poor relative brings a greater reward than giving charity to a poor person who is not a relative.
Al-Tirmidhi (658) and Ibn Maajah (1844) narrated that Salmaan ibn ‘Aamir al-Dabiy said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Charity given to a poor person is charity, but charity given to a relative is two things: charity and upholding the ties of kinship.” Classed as saheeh by al-Albaani in Saheeh Ibn Maajah.
Al-Haafiz said in Fath al-Baari:
It is not necessarily the case that a gift given to a relative is better in all situations, because there is the possibility that a poor person may be in desperate need and the other person (the relative) may not need it at all.
Giving iftaar to a relative comes under the meaning of the words of the Prophet (peace and blessings of Allaah be upon him), “Whoever gives iftaar to one who is fasting will have a reward like his,” and giving him iftaar may bring a greater reward than giving iftaar to one who is not a relative, or it may be the opposite, depending of the needs of those concerned and the interests served by giving him iftaar.
And Allaah knows best.