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.  

Conclusion: 

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.