Abstract—Although there is evidence that left ventricular (LV) function is genetically controlled, the contribution of familial factors to variation and covariation of LV diastolic filling, contractility, and structure is unknown. Single- and cross-trait sibling correlations were estimated using bivariate familial correlation models in 200 white (400 pairs) and 374 black (539 pairs) hypertensive sibships. LV transmitral early and late peak filling velocities, isovolumic relaxation time, atrial filling fraction, stress-corrected midwall shortening, and LV mass and structure were measured and adjusted for important covariates in race-specific linear regression models. Single-trait sibling correlation was strongest for early peak filling velocity. Significant cross-trait sibling correlation was detected between early and late peak filling velocities. In whites, early peak filling velocity and atrial filling fraction, and isovolumic relaxation time and end-diastolic posterior wall thickness, were also significantly correlated. Familial factors common to early and late peak filling velocities contributed to 64% and 54% of sibling resemblance in early peak filling velocity and to 76% and 77% in late peak filling velocity in blacks and whites, respectively. In whites, 100% of sibling resemblance in isovolumic relaxation time was shared by posterior wall thickness, whereas 75% of sibling influence in posterior wall thickness was common to isovolumic relaxation time. In conclusion, significant cross-trait sibling resemblance was detected between (1) early and late filling parameters and (2) isovolumic relaxation time and posterior wall thickness, suggesting pleiotropy and/or common environment on these traits. These data have potential importance in understanding heritability of LV diastolic function in hypertension.