Objectives The aim of our study is to examine the association between knowledge about the World War II (WWII)-related traumatic experiences of their ancestors and subjective well-being (SWB) of young adults, i.e., descendants of Polish survivors of WWII. Specifically, we focus on the life satisfaction and the mental, physical, and psychosocial well-being of our participants in relation to their knowledge about WWII trauma in their family histories. Method The sample comprised 500 Polish young adults recruited from a nonclinical general population. Participants first filled out a questionnaire assessing their knowledge about traumatic events that their ancestors could have experienced during WWII (see grandparents/mothers, great-grandparents/mothers). After that, subjects were given inventories to assess their SWB, i.e., the Satisfaction with Life Scale (SWLS) and the General Health Questionnaire (GHQ-28). Results Latent profile analysis was applied to extract profiles of participants differing with regard to the scope of knowledge about WWII-related traumatic experiences among ancestors. Specifically, six profiles were observed, and a general lack of knowledge about this kind of trauma in the family was characteristic of the sample. We also found differences in SWB across profiles of participants, with worse SWB in the profiles with the highest lack of knowledge about WWII-related traumatic experiences in the family. Conclusion Our study adds to the literature on intergenerational trauma by applying a person-centred perspective, a methodological approach almost invisible in research on that topic. In addition, our findings can serve as a stimulus for more comprehensive debate on WWII trauma in Polish society.