The name 'Sansenke' refers to the Omotesenke, Urasenke, and Mushanokojisenke schools of the Japanese tea ceremony. They are households descending from SEN no Shoan, who was a child from SEN no Rikyu's second wife's previous marriage, and are all of collateral lineage as opposed to the Sakaisenke which is the honke (head family).
The Sansenke was established as follows; Sosa KOSHIN, who was the third son of the third head of Omotesenke, SEN no Sotan, inherited the family estate and founded Fushin-an Omotesenke; Sotan's fourth son, Soshitsu SENSO, inherited the retreat of Sotan and founded Konnichi-an Urasenke; and the second son, Soshu ICHIO, who had been once adopted and had left the house, came back to Senke and called himself Kankyu-an Mushanokojisenke.
The seventh head of Omotesenke, Joshinsai, decided that 'those that can call themselves Senke are (the first sons of) Omotesenke, Urasenke, and Mushanokojisenke, and second sons, third sons, and so forth can't call themselves as one,' and the other two houses agreed with the decision; therefore, Senke in the world of tea ceremony came to be limited to the three houses, which are Omotesenke, Urasenke, and Mushanokojisenke.
At around this time in Kyoto, there was a custom of referring to Yabunouchi family in Shimogyo as the Shimo School and the Sansenke in Kamigyo as the Kami School, and the three households were recognized as a single school. Actually, the three households (including the Hisada family) adopted children from one another, and collaborated in developing each others institutions. It was after the Meiji period, when the continuation of tea ceremony culture came under threat, that the sansenke came to be regarded as different schools.
Family name changes
Before the World War II, it was a simple matter to change one's family name or adopt a child, and there were no problems involved in the process, but after the World War II, the civil law was revised and the permission of a family court became necessary in order to change one's family name. In 1959, Yoshiharu - a younger brother of Hounsai, the 15th head of Urasenke - proposed changing his family name as a custom and was given permission, which was followed by others including Shojiro SAKAI and Masakazu IZUMI following suit. The same custom also exists within the Ikenobo family of Kado (flower arrangement), and Senho ONO (小野専芳) also changed his family name.