I get what you are trying to achieve here. But it a bit off. Like I understand it, but I wonder if you could find a better way to relay this information that is not so wordy and drawn out.
Her’s had passed from her mother, who had died giving birth to Aelyth twenty years ago, before that it had belonged to her mother’s mother, and her mother’s mother, and her mother’s mother, and before that it did not exist as part of their song