Catching two animals in the same trap, a double capture, can provide information on social organization. House mice (Mus musculus) have not been previously studied in terms of double captures. We examined rates of double captures and effects of age, sex and density on double captures. We used DNA-based parental assignment to examine the hypothesis that double captures would differentially involve related mice more than unrelated mice. House mice were involved in double capture events less frequently than several other rodent species. Double captures accounted for only about 0.2% of all house mouse captures and only 12.6% of eligible mice were involved in double captures. Season and density influenced the rates of double captures. Pairs of juvenile males were captured together significantly more than expected, possibly because these young mice have a greater tendency to be together more while foraging or entering traps, but, without direct observation, this can only be inferred. Adult female-adult male pairs also occurred more frequently than expected, as has been reported for Peromyscus and Microtus. Unlike other rodent species in which double captures have been examined, pairs of adult males occurred with significantly lower frequency than expected, as males in the house mouse social system apparently avoided one another. Related individuals were captured together significantly more often than unrelated individuals. Adult females were caught frequently with their progeny of both sexes. Adult males were never caught with male or female progeny. These data shed light on the social and spatial systems of house mice.