Different states have different "age of consent" standards, so, depending on where you are, even 16 is sometimes acceptable. So maybe your parents committed no crime. Or maybe they did. Just because you perceive that it worked out in the end doesn't make it right, or OK for others to repeat it. I've driven drunk and nothing bad happened; it doesn't follow that driving drunk is fine. It's irresponsible and dangerous to others. So is sexual contact with people whose age you don't know.
Having sex with someone under the age of consent is, by legal definition, rape. You can reflect on how that colors your perception of your own life/choices or not, I could care less. But it isn't injustice or "to each their own" it's the law, and the law does judge.