Intergenerational exchange plays an increasing role in realizing sustainable societies. Question-answer exchanges are the trigger for individuals to initiate some intergenerational relations, and the literature has established that inquisitiveness (curiosity about something and someone different) contributes to people’s generativity and happiness. However, little is known about how children’s inquisitiveness influences their generative concern and happiness. We claim that inquisitiveness is essential for children to enhance their happiness and hypothesize that those who receive a positive response from adults tend to be inquisitive and express the signs of generativity. To empirically examine the hypothesis, we have statistically characterized inquisitiveness in relation to adult-child interaction, generativity (offering care for people and the natural environment) and happiness, using the data from a survey of 511 Japanese children between 9 and 14 years and by applying the revised generativity concern scale (GCS-R). The results show that inquisitiveness correlates with generativity and happiness, primarily that a positive response by adults to children’s inquiries promotes their inquisitiveness through adult-child interactions. Our analysis shows that children’s inquisitiveness, encouraged by adults’ positive responses, is more significant in happiness than the generativity concern during childhood. Overall, the results suggest that adults responding positively to children’s questions is essential for promoting inquisitiveness and increasing happiness.