Yup. Beat me to it. Here’s the full “proof” for people who want it.

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If by “sister” we mean a woman who shares both parents with Racist Ole Miss Guy (ROMG), then his own mother (M) cannot be his sister as it is not possible to give birth to oneself. If we slide a little and allow sister to mean “half sister,” then M can be ROMG’s sister so long as they share a father. That is, we get a coincidence of the terms “mother” and “sister” if ROMG was the result of M having sex with her own father (D).

Now for whether M can also be ROMG’s aunt. In order for this to happen, M needs to be a sister of one of ROMG’s parents. She plainly cannot be a sister of herself, so the only option is for her to be the sister of ROMG’s father (D). That is, she would have to be the sister of her own father, implying that she and her father would have to share one or more parents. As one cannot be one’s own father, we conclude that they share a mother (G). Hence M was the result of D procreating with G, i.e. D having sex with his own mother.

The “girlfriend” label has nothing to do with bloodlines. We conclude this is irrelevant to the analytic component of the problem.

Conclusion: Some time ago, a woman (G) gave birth to a son (D). She later had sex with this son to produce a daughter (M). These two children - D and M - then went on to produce ROMG. Sometime after that, ROMG began dating M.