Your cartoon brings up a possible real reason for same-sex marriage: gay men being able to “marry” teen boys. In most states, a minor may marry at 16 with parental consent (15 or younger in some states).
Ironically, I just came across a cartoon from the 1963 October Playboy that had 2 men in from of a marriage counselor with the caption of “You realize, of course, that starting out you had two strikes against you.” Playboy being, from its inception, an argument for fluid morality and hedonism, makes this a good exemplar of how things have changed. I have looked but have not found it available to show the actual cartoon!