So your saying by two consenting adults that you are speaking on a basis of the law of where ever the reader is located. I just hope this isn't the standard, or even near to it, view. See, the number one place I see that asked is in discussions of rather something sexual is moral or not. The thing is, most people here base there system of morality off of something besides the law, and often wants the law to reflect their morals and not vice versa. A good example is this, we don't make murder immoral because it is illegal, we make it illegal because it is immoral (or the act of hurting someone is, ect.). In the end, I believe/hope most hold to some undefined standard of when another is able to engage in sex and is thus able to consent, but being that this standard is mostly undefined, they use the law of the land as a crutch. That way, it is only the lack of most people realizing that this crutch is in the end the byproduct of society's (often ill-concluded) morals, and thus they are in essence 'pulling themselves up by their shoelaces'.
Please note I could easily be confusing ethical and moral, so I hope that doesn't cause any problems.
I will say that I do like the claim "competency when compared to each other is relatively equal" as it avoids a major pit hole that many are very unaware of.
And of course, those who base their morals on the legal system, those of you to whom murder is immoral because it is illegal, please ignore this whole dribble of English.