One explanation given for the gender wage gap is the division of labor in the home. On the marriage outset, averagely speaking, husbands who are older invest more human capital in market activities than wives. This paper concentrates on the age gap at first marriage. It hypothesizes that the demand for children is one important reason for the husband-wife age gap. To show this, the paper extends a two-sided matching model of marriage (originally introduced by Eugenio Giolito [1]) based on the biological fact that men have a longer fecundity horizon than women and examines cross-country data from World Marriage Patterns 2000 to show a higher marital age gap the greater the role children play in economic activities, the greater the importance of agriculture in an economy, the greater a country’s rural compared to total population, and the greater the population’s proportion of pro-natal religions.