1) Statutory rape != rape
Rape is sexual contact w/o consent. Statutory rape is a violation of legally established ages of sexual contact. Consent isn't even considered in the latter. Now, statutory rape can be considered for a 17 yr old who decides to have sex w/ a 30-something but c'mon, seriously, is 'that' rape? Both parties know the mechanics and consent to the action so 'rape' is a dubious term at best. In the OP's post, it has not been established whether they actually had sex; whether the son consented or not; and who is the source of the accusation.
2) Westermarck effect (
Wiki)
An observed phenomenon when two people who live in close domestic proximity during the first few years in the life of either one, both are desensitized to later close sexual attraction. Even were the OP post true, since neither party were close to each other, the desensitization period was never allowed to happen; thus, the possibility of attraction (while not inevitably guaranteed) was definitely increased.
3) kid's a bit of a douche, as shown in later posts
Thus it's questionable whether or not he's just started spreading rumors to get back at mom for giving him up for adoption. It wouldn't be the first time a kid did something vindictively stupid to show up an adult.
4) Males can get raped too.
Rape is defined as nonconsensual sex. That's all it takes for someone to be raped. If a woman drugged a guy and had sex w/ him, she raped him. If a woman held a man at gunpoint until he put his cock in her, she raped him. And many other myriad situations where one party isn't consenting to the sex. That simple.
EDIT:
[quote name='DestroVega']first, why would any guy need to be raped? i never understood that... how do you "get up" for a
rape?[/QUOTE]
You're presuming that a guy would need to 'get up' for rape. But guys can be penetrated too... all a woman would need is a dildo in her possession.