The purpose of this study was to examine motor proficiency relations of siblings. 23 sibling pairs ages 5 to 13 years were studied. Motor proficiency was assessed by the Bruininks-Oseretsky Test of Motor Proficiency-Short Form of 14 items, adjusting for Body Mass Index percentile, age, and sex. The association among siblings' overall motor proficiency was not statistically significant. When each of the 14 items in the test was examined separately, significant associations were found. Items positively associated among siblings included walking on a balance beam, tapping feet and making circles, and sorting shape cards. Copying a picture of overlapping pencils and making dots in circles were inversely related. The results indicate that siblings may share certain motor-skill components of balance, bilateral coordination, and upper limb speed or dexterity, but do not necessarily have the same global motor competence. Additional research is needed to explain relations in motor skills among siblings.