This study uses the tools of corpus linguistics to investigate ascending kinship terminology in the Linguistic Atlas of the Middle Rockies, a collection of interviews gathered in Colorado, Utah, and Wyoming as part of a dialectological survey of the American West. Relying in part on the framework of Dahl and Koptjevskaja-Tamm (2001), particularly with respect to their notion of a parental kin prototype, the study examines lexical and grammatical variation in the use of terms for parents and grandparents in different interviewing contexts in an effort to identify patterns in these distributions. The study finds important quantitative differences in the distribution of mother and father, as well as differences in the grammatical behavior of these and other kinship variants. While these results provide some support for a parental kin prototype, they also suggest the benefits that survey data collected within a variationist framework offer such a prototype, both with respect to the counterexamples to broad generalizations that such datasets inevitably include as well as the variable patterns that often emerge from such data that might go unobserved using formal methods.