You and the Woman you have been dating decide it's time to take things to the next level. As she unzips your jeans she discovers one tiny disappointment. How dare you waste her time for all of these months!? Knowing full well you have a tiny little pecker lurking downstairs.
Embarrassing you even further, she calls in her Son to mock and humiliate your walnut whip. They decide the ultimate revenge for you and your shrimp dick will be to watch in despair as your Girlfriend gets fucked by her own Son and his huge cock. This is all shrimp willy losers like you deserve, to be a little cuck as you're never going to get her perfect pussy.
You say it's "fucked up", but if this is the only way she can get some decent cock then so be it.