This is a feasibility study with pilot randomized controlled trial design. A convenience sample of 60 intergenerational co-parenting family units, including 60 first-time parents (60 mothers and 60 fathers) and 60 grandmothers (mother-in-law of mothers) will be recruited from the obstetric clinics in the outpatient department of the study hospital, with 30 family units of each in the intervention group and control group respectively. A sequential enrollment list linked to a random number sequence will be generated by a statistician. Participants who are recruited will be randomly assigned to the intervention or control group by a research assistant based on the sequential enrollment list. Participants in the control group will receive usual care. Those who are randomized to the intervention group will receive the intergenerational co-parenting program in addition to the usual care, including 3 weekly antenatal sessions (start from 33-35 weeks gestation) and 2 weekly postnatal sessions (start from the first week after discharge from hospital). The essential components and focus of the intergenerational co-parenting program were developed based on the themes identified from the two qualitative studies, the systematic review of co-parenting interventions, and the proposed intergenerational co-parenting model. The intervention will be delivered online through an education platform of the study hospital. The acceptability, feasibility of the intergeneration co-parenting program will be examined. In addtion, the preliminary effects of such program on the intergenerational co-parenting relationship between mothers and grandmothers reported by mothers (primary outcome), and on the secondary outcomes: the psychological well-being of parents and grandmothers, the co-parenting relationship between parents, parenting stress and parenting self-efficacy of parents at 6 weeks, and 3 months postpartum will be assessed.