This study explores the ways immigrant children interpret the migration of their mothers and the reunification in the host society. The research was based on 28 interviews with children of Latin American and East European origin who rejoined their mothers at different ages. The findings highlight that immigrant children are active agents in family reunifications and are able to (re)make and negotiate kin relations with their mothers. Even though the mother–child relationship is usually assumed to be ‘natural’ and biological kinship is considered the essential basis for the relationship, for reunited children social kinship is more important than the biological link. Kin relations with mothers are constructed in everyday life, and the outcomes can be more or less positive. The final aim is to underline how migrant children can influence kin relations within their reunited families and to gain a broader understanding of family reunification patterns.