I read through the 24 pages of this thread and I didn't find any mention of this, so I'm going to do it.
I think that Queen Lamia is not Mother, nor Double, but Venus and Aeon, are actually Lamia's daughters.
I believe that as a goddess Mother was first. Then she "gave life" to a human version of herself, whom she could command, Lamia. Following the wishes of her Godly double, Lamia gave birth to the human version of Venus and Aeon. She was happy then; she had a kingdom protected by a goddess, and 2 daughters that were given to her without intercourse (à la virgin Mary).
But, Mother, also wanted to meet "her" daughters and spend time with them, so she allowed Neferti to destroy Lamia's family and Kingdom in order for Venus and Aeon to ascend to their godly status. Once Venus and Aeon discovered that her true mother was a goddess, and that the one on earth was just a low quality copy of her, they lost all their love towards Lamia, who died in the destruction of the kingdom.
The three goddesses then created the skullheart and used the soul of the deceased Lamia to power it up, giving life to Double.