Which is why I qualified it with "...or people from his household". Perhaps owning dogs himself would have been too much of a resemblance for Heinrich, but he was okay with either of the Roche-Raymons or someone else from his circle and household owning them. Now that I think of it: Fontane mentions that the Countess de la Roche-Raymon as an excentric old lady was a major major cat lady (with some other animals in her apartment, too, when he visited), who in fact died by bite of cat. Presumably she already liked cats as a young woman, and she and her husband were living with Heinrich part of the year, so the cats at least probably were hers.