It is not only his kindred, or the Arabs, but all humanity:
"And We have not sent you except as a giver of glad tidings and a warner to all mankind, but most of the people know not"
(Saba’ 34: 28)
Such capacity for preaching the Message to all emanates from the Prophet’s special capacity for loving and caring for all, “I am sent to every red and black person.” (Sahih Muslim) By the red the Prophet (pbuh) meant the non-Arabs, and by the black he (pbuh) meant the Arabs.
This is the essence of the universality of his Message. It is not an expression of dominion or a desire for supremacy, but an innate love of goodness for all beings. Nothing is more indicative of this than his sincere words:
“I am sent to all people; and if they do not respond to me, then to the Arabs; and if they do not respond to me, then to the Quraish; and if they do not respond to me, then to Banu Hashim; and if they do not respond to me, then to myself alone.”
(As-Saghir fi Ahadith Al-Bashir An-Nadhir, Hadith no. 3147.)
The Prophet (pbuh) is simply calling those whom he loves to goodness. If they respond to him, his happiness and theirs is great; and if they do not, he (pbuh) has honored his duty and conveyed the Message, leaving people no excuse before their Lord. Lest you say:
“There came unto us no bringer of glad tidings and no warner.”
(Al-Ma’idah 5: 19)