Robert, look around. People are able to marry at 14, and younger, in this country. Minimum ages are different from state to state, but Massachusetts allows girls to marry at 12 with parental consent; in New Hampshire it's 13.
Do I think people in this country are generally ready for marriage at 14? Of course not. But I think the reason is nurture, not nature. Most people in this country don't seem ready for marriage when the law allows it. Raise children the way they were raised in an agrarian society, 200 years ago, and you'd be dealing with a very different population.
Interestingly, the Amish seem to wait until 20 or so to get married. I would have thought they would marry earlier. Perhaps the reasons are economic.
Obviously, since I don't think 14-year-olds are generally ready for marriage, any interest in someone that young suggests a psychopathology -- though it is not conclusive. Psychologists distinguish between adults who are attracted to minors before puberty and after. The former are considered pedophiles; the latter are not.
If you want to read more on the subject, there is a Wikipedia article entitled "Child marriage in the United States." The facts may surprise you.
It might also surprise you to know that first cousins can marry legally in around half the states in the US. Many people consider it incestuous; but first cousins being free to marry has been the norm throughout recorded history. The prohibition is the exception. Edgar Allen Poe married his first cousin when he was 27 and she was 13.