 Sōtan had his fourth and youngest son, Sensō Sōshitsu, adopted into the family of a doctor, but after a few years the doctor died and so Sōshitsu returned to live with Sōtan.Eventually, he became heir to the retirement quarters, and the family there came to be known as the Urasenke (rear Sen house/family).Also, among Sōtan's chanoyu followers, there were four who were especially close and active in the world of chanoyu.