Background and Objectives: Relatively little research investigated whether experiences during young adulthood have long-lasting consequences for older age loneliness. This article examines whether deviations from culturally based scripts regarding family transitions represent risk factors for later-life loneliness. Moreover, it analyzes whether and in which conditions long-term associations between family transitions and loneliness differ across nations. Research Design and Methods: The analyses use micro-level data from the Generations and Gender Survey Wave 1 for 12 European countries. The sample comprises 61,082 individuals aged 50-85. The research questions are addressed using a step-wise approach based on linear regression analyses, meta-analyses, and meta-regressions. Results: Results show that never having lived with a partner and childlessness are most strongly related to later-life loneliness. Whereas early transitions are unrelated to later-life loneliness, the postponement of partnership, and parenthood are associated with higher levels of loneliness compared to having experienced these transitions "on-time". Childlessness is more strongly associated with later-life loneliness in more traditionalist countries than in less traditionalist ones. Discussion and Implications: This study reveals that individuals with non-normative family transitions are more exposed to loneliness in old age, and that this exposure is related to societal context. In traditionalist contexts, where people rely on families for support, older adults who have experienced non-normative family behavior, and childlessness in particular, may be particularly at risk of loneliness.