This article examines the ways in which early medieval genealogical texts might be augmented over time in order to reflect changing political situations. Two early ninth-century tracts from the kingdoms of Powys and Dyfed in Wales are taken as case studies. Textual and chronological problems with the tracts are discussed, and contexts are proposed for the circumstances of their composition. It is suggested that each of these tracts stands at the head of a process of ‘pedigree growth’, whereby, during the course of textual transmission, the genealogical content of each tract was extended both backwards and forwards in time.