The purpose of this study was to investigate the effect of family characteristics of the baby boomer generation on the level of their later life preparation. This study randomly sampled a birth cohort between 1955 and 1963 consisting of participants living in Seoul, South Korea with a spouse and a child/children. This study investigated a total of 455 subjects from March 2 to March 20, 2016. The study findings are summarized as follows. This study analyzed the characteristics of baby boomers' family relationships and their effects on their later life preparation. It was found that 55.4% of the subjects had at least 2 children, and 44.6% had 1 child. Concerning their children's marital status, 33.8% had married children and 66.2% had unmarried children. The level of their children's support was found at 2.82 points (standard deviation [SD] = .64), which is slightly higher than the mean value of 2.5. The spouse satisfaction among the subjects was found to be 3.59 (.79) which is higher than the mean value of 3. The general status of later life preparation was 2.70 (SD = .44), which is lower than the mean value of 3. In the sub-dimension, the level of social preparation was 2.98 points (SD = .61); the level of economic preparation was 2.60 (SD = .64); and the level of physical preparation was 2.53 (SD = .45). All the values were lower than the mean value of 3. The overall status of later life preparation of the subjects in this study was low. The physical preparation level was particularly low. To analyze the factors that affect baby boomers' later life preparation, a hierarchical regression analysis was implemented. As a result, a significant effect was found in specific factors, such as spouse satisfaction (${\beta}$ = .32, p < .001), age (${\beta}$ = .26, p < .001), number of children (${\beta}$ = -.18, p <.001), health status (${\beta}$ = .18, p < .001), gender (${\beta}$ = -.11, p < .05), household income (${\beta}$ = .10, p < .05), and children's marital status (${\beta}$ = .10, p < .05). That is, the higher the spousal satisfaction, the older the age, and the lower the number of children, the higher the levels of later life preparation. Further, a higher level of later life preparation was observed in women, those with higher household incomes, and those with married children.