The current study examined effects of representations of relationships with parents on young adults’ representations of romantic relationships and self-esteem, with particular attention paid to the role of fathers, instability of representations, and bidirectional effects. Data were obtained from two waves (Waves 4 and 5) of a five-wave study. At wave 4, 287 young adults (mean age = 20) participated, and at Wave 5, 276 young adults (mean age = 22) participated. One-time interviews (Behavioral Systems Questionnaires; BSQ) were conducted to measure the level of representations of relationships with parents. Nightly diary checklists (7 nights at Wave 4, and 5 nights at Wave 5) were used to measure the level and instability of representations of romantic relationships (BSQ) and self-esteem (Rosenberg Self Esteem Scale). Two styles of representations, including secure versus dismissing (e.g., relying on parents or romantic partners when distressed versus not relying on them) and preoccupied (e.g., worrying about rejection and excessive dependency) were measured for relationships with parents and romantic partners. The results showed evidence for unique roles of fathers, instability of representations, and bidirectional effects. Relationships with fathers affected young adults’ self-esteem. More nightly fluctuations in security with romantic partners predicted higher levels of security with romantic partners, but only in the context of more secure relationships. More nightly fluctuations in self-esteem predicted more dismissive representations of fathers. Bidirectional effects involved young adults’ representations of both romantic relationships and self-esteem, and their representations of relationships with parents. The relation between instability of representations of romantic relationships and later security in romantic relationships might represent learning about romantic relationships. The relation between instability of self-esteem and later dismissive styles with fathers (e.g., not relying on fathers when distressed) at this age might be an indication of learning to become autonomous from fathers. Finally, I also hypothesize that during emerging adulthood, fathers tend to encourage children to solve their stress or problems by themselves, while mothers tend to still provide help when children are distressed. These suggested hypotheses should be examined in future research.