Four papers investigate the neural signatures of close other representations in young and older adults. The first paper connects neuroimaging and attachment theory within a novel social, cognitive, and affective framework. Attachment theory is applied to understand why we would expect cognitive representations of close others to be different from other social neural representations. Existing neuroimaging literature on close other representations is examined, highlighting the recruitment of neural systems supporting reward, motivation, and distress alleviation, in addition to the mirror neuron system, default network, and salience network. Methodologies of past studies are reviewed, revealing a diverse array of self-report measures assessing closeness and social cognitive tasks that, taken together, preclude meaningful synthesis of findings. Specific behavioral measures of attachment are discussed, with recommendations for the field. The second paper examines the neural representation of known others along a continuum of attachment using fMRI. Heterosexual adults in romantic relationships for more than two years, made trait judgments for various social targets. Across conditions, trait judgments engaged the default network and lateral prefrontal cortex. Judgments about oneself and a partner were associated with a common activation pattern encompassing anterior and middle cingulate, posterior superior temporal sulcus, as well as anterior insula. These results provide novel evidence that mentalizing about known familiar others results in differential brain activity and that adult attachment is a distinguishing feature of these differences. The third paper investigates the neural representation of known others in young and older adults, using the same trait judgment fMRI paradigm. Across both age groups, all trait judgments engaged default network regions such as dorsal and ventral medial prefrontal cortex and posterior cingulate cortex; however, older adults showed a lack of neural differentiation between social conditions. Both age groups demonstrated connectivity between dorsal and ventral medial prefrontal cortex and other default network regions during trait judgments. However, older but not young adults also showed increased functional coupling between medial and lateral prefrontal brain regions. Results extend the dedifferentiation and default – executive coupling accounts of neurocognitive aging to social aging neuroscience. The fourth paper examines the neural representation specifically of parents and adult children, again using a trait judgment task in fMRI. Higher levels of parent and child attachment were associated with lower neural recruitment in anterior cingulate cortex, amygdala, posterior cingulate cortex, medial temporal lobe, and occipital face area. Results provide novel evidence for neural signatures of chronic accessibility, as bringing to mind one’s attached parent or child requires less engagement of brain regions involved in distress relief, memory, and facial processing. Taken together, the present studies utilize fMRI methods to contribute to an emergent neuroscience of close relationships and attachment.