The second theory says that 25 is old enough. If both people in a couple are at least 25 years old and of ‘normal’ maturity (not Paris Hilton), then I have nothing to complain about unless I know something specific about the pair. It’s a question of maturity, or rather of ‘callowness’. If someone 35 wants to go with or marry someone 19, then I am concerned, because almost any 19-year-old is going to be ‘callow’, and why is this 35-year-old interested in someone ‘callow’? I have known of one case where the person was 23 or 24 and seemed well past the callow stage, but it’s an outlier, I think.
I have no general theory regarding people who are under 25 forming a couple with someone under 25 or only a little over 25.
I’ve had a lot of years to think about this theory of the age 25, since learning of it. It’s also around that age that physical development is completed.