"No, she’s right, Hermione. Sometimes I forget that you’re a muggleborn." Hermione bristled at the comment, but Tonks didn’t let it stop her, "Triads were very commonplace up until the First Wizarding War, when it slowly fell out of fashion. Mum told me that it was even more common in pureblood households when there were two houses that needed to produce heirs," Tonks added. 