Can you update the link to one that supports the point? The link covers many important things but barely touches on unpaid work within the home--there is one graph, which uses data from 2014 (things change!), doesn't account for employment status, includes unpaid work outside the home, and comes up with an answer of 60%, not double, for the U.S. (I'm not sure which country you mean.)

One possible source, for the U.S., is this Pew Research study. It does actually have the data for roughly-equal-earner parents. The answer is 55%, not 2x, though.

Anyway, good to include sources! But it's better if they clearly support what you say.