Parenting stress, parent–child literacy activities, and pre-schoolers’ reading interest: the moderation role of child number in Chinese families

China replaced the Two-Child Policy with the Three-Child Policy in 2021 to raise birth rates, but the potential effects of the increased number of children on family life and child development have not been empirically explored. This study examines the moderating role of child number in the relationships between parenting stress, parent–child literacy activities, and young children’s reading interest in the new Three-Child Policy context in China. A sample of 895 Chinese families was randomly recruited from a coastal city in southeastern China: one-child families (N_one-child = 359, M_age = 5.0, SD = 0.9), two-child families (N_two-child = 469, M_age = 5.1, SD = 0.9), and three-child and above families (N_{three-child and above} = 67, M_age = 5.2, SD = 1.0). The participants completed the Parenting Stress Index-Short Form, the Parent-Child Literacy Activities Scale, and the Children’s Reading Interest Questionnaire. The results showed that (1) parents with more children had higher levels of parenting stress; (2) no significant differences existed in children’s reading interest between families with different numbers of children; (3) parent–child literacy activities mediated the relationship between parenting stress and children’s reading interest; (4) child number moderated the mediating effect of parent–child literacy activities in the relationship between parenting stress and children’s reading interest, even after adjusting for child age, gender, and family socioeconomic status (SES). Overall, this study demonstrated how the increased number of children would interact with the family system concerning early childhood literacy development.