In the Roman legends, the supreme deity who ruled over almost everything was named Jupiter, as was the brightest object in their night sky besides the moon, which was the planet of the same name. The Greeks, who were really the brains and philosophy behind the Romans, called this god Zeus.
In the beginning, there was Chaos. Then, a host of things were born from Chaos spontaneously, including Gaea, the earth, Tartarus, the underworld, Eros, the god of love and attraction, and so on and so forth. Gaea gave birth to the sky (Uranus), the Mountains, and the sea (Pontus). Uranus became Gaea's mate, and soon they produced the Titans, the Cyclopes, and the Hecatoncheires. Uranus really hated the three Hecatoncheires, who had fifty heads and 100 arms apiece! In a fit of rage, he shoved them back into Gaea's womb. Needless to say, this didn't make Gaea too happy. So she and her son, the Titan Cronos (Saturn in Roman myth), plotted to overthrow Uranus. With a flint sickle, Cronos castrated his father's genetalia, and Uranus fell from power. Cronos took over, with Rhea, his Titaness sister, as his bride.
Gaea and Uranus had forseen that Cronos would be dethroned by one of his own sons, as well. So Cronos took every child that Rhea gave birth to and ate it. This didn't make Rhea too happy, so she bore her sixth child, Zeus, secretly. In his place, Rhea gave Cronos a stone to swallow. Zeus, in the meantime, was sent to the island of Crete to grow up. Eventually, Zeus was able to return, free his other five siblings who had been swallowed (plus the rock), and give Cronos the boot. The other Titans were sort of power-hungery, too. Zeus, his brothers and sisters, the Cyclopes, and the Hecatoncheires fought them off in an epic, earth-shattering battle. Finally, Zeus was seated into power atop Mount Olympus. The Cyclopes, as a gift to his valor, gave Zeus the power of thunder and lightening.
Zeus was first noted as the storm god, who wielded the thunderbolt on high. Note that Sailor Jupiter's powers also deal with thunder. Zeus also came to be the most powerful god, though Uranus was, at one time, his better. Therefore, using Greek mythological evidence, it can be concluded that Jupiter is really the more powerful senshi.
Zeus, as most people know, was a womanizer. A BIG womanizer. Could this be tied to Makoto's boy-craze? You decide. At any rate, Zeus impregnated many mortal women with hybrid babies. Well, many immortal women, too. But one of the mortals was a woman by the name of Leda. Leda, Lita. Hmmmmm... Anyway, Zeus came to Leda in the form of a swan, and shortly after, Leda laid a swan egg, out of which hatched Helen and Clytemnestra, and Castor and Polydeuces. However, Leda's husband, King Tyndareus, had slept with her about the same time, so he thought the kids were his. I don't know, maybe all babies hatched from swan eggs back then.
Anyway, much much later, there was another one of those "relatives killing one another for the throne and sleeping with whoever's wife so that the son, who's really his brother, comes back and fufills the prophecy etc." things in the House of Atreus. It's very much a reoccuring theme in Greek mythology, but let's cut to the good part. King Pelops was the ruler of Peloponnesus. He had a beautiful wife by the name of Hippodamia, and they bore many children. Pelops, however, liked his bastard son Chrysippus the most. Hippodamia bagan to fear that Pelops would give Chrysippus the throne and not one of her own children, so she murdered him. By doing so, she framed two of her sons, Atreus and Thyestes. Not wanting to be accused of this murder, they fled to Mycenae. Atreus aquired the golden fleece there, which would have established his right to rule. His brother, however, slipped into bed with Atreus's wife, Aerope, and got the fleece from her. So Thyestes was now established as king. He made a deal with Atreus, however. He said that if the sun moved backward in its course, Atreus could be king. So what happened? The sun moved backward.
Re-established as the rightful king of Mycenae, Atreus had two sons with Aerope: Agamemnon and Menalaus. He also vowed revenge on Thyestes for stealing the fleece and his wife. So he cooked up Thyestes' sons and served them as a banquet to him. Yummy!
Now Thyestes was a little pissed. He asked the gods what he could do to get even. He was told to father a child with his own daughter, Pelopia. So he jumped on her one night and got her pregnant. As fate would have it, Atreus found Pelopia not long after and made her his wife. So Atreus assumed that the child Pelopia gave birth to, Aegisthus, was his own.
To make a long story less long, Aegisthus found out that Thyestes was his real father. In a fit of rage, he killed Atreus for being a poser. Pelopia commited suicide when Aegisthus found out. So Thyestes was king again, while Atreus's sons, Agamemnon and Menelaus, went into exile.
Ack, exiled sons, again. And guess what they wanted to do. Get to power and overthrow their father! So they sought the help of King Tyndareus (you know, Leda's husband?). Thydareus restored Agamemnon to the throne of Mycenae, and married Clytemnestra, one of the daughters of Zeus and Leda. Menelaus took Helen as his wife and ruled Sparta.
You may know Helen better as Helen of Troy. She was the cause of the Trojan War, actually. Paris, the Trojan prince, kidnapped Helen because she was the most beautiful woman in the world. So they started a war over her.
And what about Clytemnestra? Well, she didn't like Agamemnon much, because he killed her first husband, sacrificed their daughter to Artemis, and took a number of mistresses. So she took Aegisthus (you know, Thyestes's son that slew Atreus?) lover and plotted to kill Agamemnon. They did. Clytemnestra killed Agamemnon's new mistress while Aegisthus killed Agamemnon. There's more to that story, but I could be pursuing stories all day. So I won't.
But I will tell you what happened with the two sons that were born from Leda's egg. Castor and Polydeuces were famous twins who protected sailors. They also showed a strong brotherly link for one another, so they have come to be known as the ultimate symbol of sibling affection.
So borne from Zeus, god of lightning and thunder, and Leda, were Helen, known for her extravagant beauty; Clytemnestra, who wouldn't take cr*p from Agamemnon and his new chick; and two figures of togetherness who protected sailors. Don't all of these qualities pertain to Kino Makoto and Sailor Jupiter? Or is it merely coincidence? I'll let you be the judge of that.