There is very little evidence of any negative correlations - opposites do not, on average, attract. B. Household production is cleaning, cooking, shopping, caring for children, and all of the other chores people do when they aren't working for others. If the lower-wage labor is actually better at household production. There are fixed costs of working - like commuting time. In principle, either the husband or wife could be the higher-earner.
Children reduce women's job experience and interrupt their careers.
Anticipating this, women have weaker incentives to accumulate human capital. When needs for household production are large, there is a firm economic rationale for the traditional family, where the male earns almost all of the income and the female does almost all of the household production. The family needs one person to do household production and another to hold down a job. If both are equally able to do household production, it makes sense for the higher-paid person to work outside the home. If women anticipate this, they invest less human capital, making the wage gap larger.