The aim of the present study was to examine the relationships between personality metatraits, the structure of childhood parental relationship boundaries, and Young’s disconnection and rejection schemas, in the context of their potential role in shaping loneliness as a social phenomenon. It was assumed that personality metatraits would serve as the primary predictors of schemas, whereas early relational experiences with parents would moderate this association. The study was conducted on a sample of 404 adults. Participants completed the following instruments: the CPM-Q-SF Personality Questionnaire, the Family Environment Analysis (RP-Mother, RP-Father), and the Young Schema Questionnaire (YSQ-S3). Data were analyzed using hierarchical linear regression in the R statistical environment. The findings revealed a significant association between the Disharmony metatrait and the intensity of the Emotional Deprivation, Social Isolation, and Defectiveness/Shame schemas. This effect was particularly pronounced in participants who reported rigid maternal boundaries. The results highlight the importance of the interaction between personality vulnerability and early relational experiences in the development of schemas related to instability and insecurity in interpersonal relationships. The data provide an important contribution to ongoing discussion of the psychological mechanisms underlying loneliness, as well as the difficulties individuals face in forming and maintaining close, lasting relationships. In this light, the findings may inform the development of preventive and therapeutic interventions, particularly in addressing the growing phenomenon of social isolation and loneliness.