Semantic distinctions are encoded variably in kinship terminology, the set of words that denotes family members. Nonetheless, it has been suggested that kinship terminology, like other linguistic domains, is constrained by opposing pressures to be simple yet expressive. Here, we use this insight to explore how the meaning space for kinship is structured cross-linguistically. Under the assumption that kinship systems map forms to meanings in a compressible, structure-preserving manner, we designed a metric for identifying which semantic features are most important for distinguishing individuals in a kinship system. For 1229 kinship systems, we calculated the correlation between semantic similarity (the weighted sum of shared semantic features between individuals) and wordform similarity (the edit similarity between terms). We then identified the optimal weight for each semantic feature in each language, confirming that kinship systems vary in which semantic features they encode, and that the features themselves vary in the extent to which they are encoded. Additionally, we identified that semantic features are encoded hierarchically; more simple and more informative features are weighted highest in general. By identifying this constraint on the distribution of forms and meanings in kinship terminology, our results provide new insights on how kin terms are structured for efficient communication.