Grammi was a former servant of Layla Heartfilia and the mother of Brandish μ.

Sometime after Layla had retired from being a Celestial Spirit Mage, Grammi was given Aquarius's gate key, which she treasured dearly, polishing it every day until it shone without fail. After Aquarius' key was handed down to her, she traveled the world to the continent of Alakitasia, making it so that Layla was unable to contact her to retrieve the key in order to open the Eclipse Gate in correspondence with the latter's clan formed from 400 years in the past. Unfortunately she couldn't be found, forcing Layla to compensate for Aquarius' key using her life force. Layla then fell ill with Magic deficiency disease; it was not until 7 days after the news had finally reached Grammi's ears with her returning to Ishgar. Grammi blamed herself for what had happened to Layla and returned Aquarius' key because she thought she was no longer worthy of possessing it. On her way back home, Zoldeo snuck up behind her and stabbed her with a knife. Zoldeo blamed her for Layla's ill-being, which Grammi concurred and blamed herself, but requested of him one last favor—to not harm Brandish for her own misdeeds. Grammi later passed away due to the fatal injuries she had sustained.
(Source: Fairy Tail Wikia)