[1] The eldest son of Japanese foreign minister Yōsuke Matsuoka, Kenichiro was born in the United States while his father was First Secretary of the Embassy of Japan, Washington, D.C., attended Gyōsei High School and Tokyo Imperial University, majoring in Political Science and Law.

[5][6][7][8] [9] NET courted Matsuoka for his knowledge of foreign culture and fluency in English and French, having been born in the United States, studied in Paris, and experienced with Man'ei.

He was able to watch foreign programming in its original format and was responsible for licensing Rawhide and Laramie, gaining high ratings for the new network, and giving them an advantage over rivals NHK and Fuji TV.

[17] Kenichiro's mother Ryuko, was the daughter of an influential kuge judge Shin Soroku, a former retainer of the Chōshū clan, and a beneficiary of their outsized influence in the Meiji Restoration that helped shaped the modern Japanese Government.

Kenichiro is related to the royal family through Kacho Haruko, the daughter of Marquis Fushiminomiya Hironobuo and Princess Kaninnomiya Hanako, and was once considered as a potential match for then Crown Prince Akihito.