what if both sets of parents know that two people are having sex at different ages, but they are fine with it because they practice safe sex with condoms? can the older of the two still be placed in prison even if the parents do not wish they be?

A parent does not have legal authority to give consent to a minor child to violate state laws.

In fact, a parent can be found in violation of state law if they are condoning or encouraging a minor to have illegal sexual relations. The statutory rape laws are just like all other state laws. If you violate them and get caught, you will be prosecuted and a parents consent will not stop the prosecution.