From Marpa, the philosophy of Mahāmudrā and the practices of Nāropa passed to Milarepa, and from Milarepa to Gampopa, who had also studied in the Kadam tradition. It is only with Gampopa that one can begin to talk of a Kagyü ‘school’, and this immediately split into four subschools, the Tshal, Baram, Karma, and Druk. Today there are many Kagyü subschools, the two most important of which are the Druk (ʾbrug) Kagyü, founded by Yeshe Dorje (1161–1211), which became the dominant tradition in Bhutan, even giving its name to that country, and the Karma Kagyü, established by Düsum Chempa (1110–93), the first Gyalwa Karmapa hierarch, and which is generally today the dominant Kagyü school.
"Kagyü." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (September 19, 2018). http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/kagyu
"Kagyü." The Concise Oxford Dictionary of World Religions. . Retrieved September 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/kagyu