So Kenny finally found his one true love.
But he can't be with her because it's illegal to marry your sister.
So Kenny finally found his one true love.
But he can't be with her because it's illegal to marry your sister.
The joke plays on the shock value of incest, which is a taboo subject. Kenny finding love is presented innocently, but then the punchline reveals that his love interest is his sister, making their relationship illegal and inappropriate. This creates a dark, uncomfortable humor.