Gather photos of the people your child sees regularly, including pets and people who live elsewhere.
Go through them naming each one and saying one true thing: 'that is Grandma. She makes the good soup.'
Then ask who is missing, or who lives in this house and who visits. Sorting people into groups is where belonging becomes explicit.
Working out who belongs to their circle, and how, is how a young child builds a map of their social world. Attaching one concrete detail to each person makes them a character rather than a label, which is what makes the map memorable.