Btw, your perception is a good one. McAvoy's character is named "Leto" or "Leto II" (to distinguish from his grandfather). Leto's twin sister is Ghanima. Ghanima means "spoil of war" in the Fremen language (and is the same in our Arabic), as she is the daughter of Paul and his concubine, the Fremen Chani, who was Paul's love match and not his "official"/courtly wife.

It would not surprise me to find as well that Herbert was playing with words and that "Ghanima" was meant also to imply "Ganymede", the most beautiful of all mortals who was made Zeus' cup bearer. And is also Jupiter's largest moon. Paul is Paul Atreides. Atreides = Atreus, King of Mycenae. The Harkonnen should to my eye be viewed as the Family that represents Cronos/Saturn/Satan, and the Atreides the Family that represents Jupiter/Japetus... the Sky Father. Indeed their heraldry includes a hawk. I see this as a hat tip to Jupiter, Zeus, and even Horus of Egyptian mythology. All the same entity. The Song Remains the Same.

An additional point: twins were and are considered to be special, in humanity in general, but also in mythology.

Leto in Greek mythology is a female, and Ganymede is a male. In Greek mythology they are not related. But both are both loved and cursed by the gods. I expect Herbert had some intention, in choosing these names. And had some fun playing with them, and subverting the original stories to his Dune narrative.

Dune is the story of Gilgamesh. Or Jesus. Or Lawrence of Arabia.

Or, more accurately, it is all of those stories.

The Song Remains the Same.

Abou Ben Adhem, by Leigh Hunt

Abou Ben Adhem (may his tribe increase!) Awoke one night from a deep dream of peace, And saw, within the moonlight in his room, Making it rich, and like a lily in bloom, An angel writing in a book of gold:— Exceeding peace had made Ben Adhem bold, And to the presence in the room he said, "What writest thou?"—The vision raised its head, And with a look made of all sweet accord, Answered, "The names of those who love the Lord." "And is mine one?" said Abou. "Nay, not so," Replied the angel. Abou spoke more low, But cheerly still; and said, "I pray thee, then, Write me as one that loves his fellow men."

The angel wrote, and vanished. The next night It came again with a great wakening light, And showed the names whom love of God had blest, And lo! Ben Adhem's name led all the rest.