Check out Farnham's Freehold, where a middle-aged man gets flung into the far future with his wife, daughter, and daughter's friend (and another guy). The wife goes crazy, and then the middle-aged man knocks up his daughter's friend. Then his daughter mentions to him that, of the men she's been stranded with, he's the one she'd prefer to father her child (if she weren't already pregnant). Her dad is completely undisturbed and in fact flattered by this.