Ask A Man 06 Aug '26: 'My partner thinks I'm sleeping with my sister.'

Anonymous’ younger half-sister recently moved to his house as she could no longer live at res.  However, his girlfriend has expressed that she’s uncomfortable with him living with his sister suspecting that he might have an affair with his sister.  They fought about this and are now not really on speaking terms. He’s offended by this and doesn’t understand why his partner is reacting this way.