Previous research has found that words are replaced faster in language vocabularies the less the word is used, whereas words that are used more frequently endure longer. Drawing from this theory, the authors of this article propose two questions: 1) Is the rate of replacement for Indo-European kinship terms correlated with their usage frequency? 2) How does this relationship differ between kinship terms and core vocabulary? Using phylogenetic comparative methods to analyze 10 kinship categories from 47 Indo-European languages, the authors find that more frequently used kinship terms tend to be replaced at a much slower rate than less frequently used words. Furthermore, this relationship between word replacement rate and usage frequency is stronger for kinship terms than it is for core vocabulary terms.