yes i have also read this too in the book called Hekate: Goddess of Witches by Courtney Weber. Although i am only 1/3 of the way through the book, the goddess are mentioned on many occasions. This might help you connect the three as one or worship them separately according to you r own interpretation. This is as different witches and different cultures too have different stories of the goddesses, who they are and how they are related to each other. For now i have (in my own interpretation) Hekate is the daughter of the goddess Asteria and the titan Perses, and Zeus honored her above all the others as the goddess of the crossroads, magic, witchcraft, the moon and wilderness. Hekate was sent out by Zeus to search for Persephone (Zeus’ and Demeter’s daughter). I also have read some witches refer to her as the direct child of Zeus as well so you can decide what you want to base your beliefs on…
Siofra gave you some great sources here within the forum! I think you might also want to check out Theoi.com for all beings Greek. They’ve got pages and pages of historical information, stories, etc. that might also help you out.
Thank you so very much for all the links for more information!