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).
千利休の後妻の連れ子である千少庵系統の家であり、本家の堺千家に対して傍系に当たる。