In mice, parental behaviour is controlled by brain-wide circuits, the functional organisation of which is increasingly well understood. However, the relevance and function of these circuits in early life remains unknown. Here, we uncover the functional circuit architecture of parental circuits in juvenile mice and address whether they control alloparental social interactions at this age. We have observed that juvenile mice start to display spontaneous alloparental behaviour between postnatal day (P) 14 and 15, at levels similar to adult virgin females. C-Fos mapping revealed that this behaviour recruits galanin-expressing neurons in the medial preoptic area (MPOAGal neurons). We confirm that these neurons start exhibiting pup-evoked activity at P15, using in vivo calcium imaging. While anterograde viral tracing from MPOAGal neurons in juveniles shows adult-like projection patterns, retrograde trans-synaptic tracing uncovers much more extensive inputs in juveniles. We find that MPOAGalneurons undergo extensive morphological remodelling between P14 and P15, accompanied by an increased frequency of spontaneous postsynaptic currents. This suggests that maturation of parenting-relevant synaptic inputs drives the onset of alloparental behaviour during this period. We are currently investigating the mechanisms underlying this cellular remodelling. Our results indicate that morphological and biophysical alterations in juvenile MPOAGal neurons contribute to the onset of alloparental behaviour. This work provides valuable insights into the neurodevelopmental processes that underlie the expression of caregiving behaviours during early life.