Since Nathan was 15 and Stuart was in his late 20's early 30s... Rape???

Depends upon the State. Most States the age of consent is 16, though some are 17 and a few are 18. However if the older partner is an authority figure to the younger, such as a teacher, minister, etc. then it is 18 in many States. For many States if the age difference between the older & younger partner is 3 years or less then consent is presumed even if the younger is under the age of consent. However, if the younger is 12 or younger then statutory rape is automatic, though for some States 13 is the operative age. Lying about age by the younger is not typically a defense for the older. Crossing from one State to another where age of consent is more favorable is also not a defense, the State of residence of the younger typically prevails. There is also prosecutorial discretion that could affect whether charges are filed. While the law across States are rapidly becoming gender neutral, for some jurisdictions prosecutors may come down heavier on same sex partners.

There was one notorious case where both boys met in high school, had consensual sex for more than a year, maybe even two. Both sets of parents knew they were boyfriends, even had them over together for dinners, etc. As soon as the older turned 18 the parents of the younger filed a complaint, with the older successfully prosecuted for statutory rape of the younger and imprisoned. The case was one of several that prompted the State legislature to enact a 3 years between partners exemption to age of consent laws but the law was not made retroactive. I believe the imprisoned partner was eventually paroled or might even been pardoned by the Governor but he was in adult prison for quite awhile, years, before his case was resolved.