This special issue aims to bolster important research that has been inconsistently and rather scarcely conducted in the past 35 years: the role that multiple caregivers jointly play in the developmental trajectories of children. Despite theoretically and empirically driven calls to assess children's development through the lenses of simultaneous and independent attachment relationships (van IJzendoorn & Tavecchio et al., 1987;van IJzendoorn et al., 1992), attachment research has predominantly focused on mother-child relationships, deeming other caretakers, at best, as subsidiary attachment figures with a marginal influence on the child's development. This special issue aims to expand on the topic by providing historical, ethological, cross-cultural, clinical, methodological, and legal perspectives on the matter.This special issue opens with a review paper by Dagan and Sagi-Schwartz ( 2021), who briefly present an historical account of the nonlinear shift in attachment theory and research, from a wide interest in assessing almost exclusively mother-child attachment relationships, to assessing father-child attachment patterns, and leading up to the current increase in interest and empirical work on attachment network to multiple caregivers. The authors also revisit their recent proposed attachment network assessment models (Dagan & Sagi-Schwartz, 2018, 2020. Karaskiewicz et al. (2021) present an ethological study on the network of attachment in mother-father-infant titi monkey (Plecturocebus cupreus) triads. The authors assessed the change in pair bonding quality before and after the couples' first offspring birth. They show that affiliation between the parents significantly decreased after birth of the first offspring and stayed relatively low even after infants' transition to behavioral independence, with multiple factors contributing to variability in such pair bonding trajectories. Importantly, Karaskiewicz and colleagues highlight a unique perspective on how new members of the attachment network (i.e., newborns) can influence the relationship quality between its existing members (e.g., mothers and fathers).The meta-analysis by Deneault et al. (2021) quantifies the associations between fatherchild attachment and behavior problems across 15 studies. The authors report two intriguing results. The first is that insecure child-father attachment is significantly associated with higher internalizing and externalizing behavior problems compared with secure dyads. The second surprising finding revealed that the effect sizes for insecure child-father attachment are equivalent to those reported in previous meta-analyses on child-mother attachment in relation to behavior problems.The individual participant data meta-analysis by expands on Deneault and colleagues' study-level meta-analysis by examining the associations between attachment networks to mothers and fathers and behavior problems. This study indicates