If she is 20 years younger, then he will have to date her until she is 18 or so, but that's okay, too. Mother nature and the lawyers agree: A women of 18 is old enough to get married, have kids, and do well at both.
Plato and many American states agree: A women of 16 is old enough to get married, have kids
Plato would even add the "and do well at both".
That is advice from a famous philosopher. He thought 16 was ideal for women, and 30 was ideal for men. I have no idea if he might have had a personal bias in that matter.
While I place no trust in Plato's reasoning or evidence, I don't see the issue as "moral". Instead, I see the importance of good family formation, which the US is failing at (birth rate so low we are rapidly going extinct, literally -- the most basic failing of a society), and needing solutions good in all or nearly all respects.
Failing at family formation is no darned good and worse -- it canNOT last. On this point f'get about Plato, Fromm, or me and, instead, listen to Darwin -- yup, he's on the case.
WTF is this comment.
Please do not take this advice.