As far as I'm aware, the Somali tribe in Kenya has at least 4 sub tribes or clans: the Ogaden, the Degodia, the Ajuran and the Garreh. Sometimes there's talk of the Garreh-Ajuran clan, even when they are apparently still distinghuised as seperate groups.
Of course, most Somali tribes live in Somalia - only half a million Somalis live in Kenya. This is because the states in Africa are relatively young and drawn up by European colonizers in the 19th and 20th century. Many African tribes live in several countries (like the Masai who live in Kenya and Tanzania).
Here's a handy map of the main Somali tribes in all of East Africa:
http://www.lib.utexas.edu/maps/africa/somalia_ethnic_grps_2002.jpg
