Jupiter

[Koen G]

That may be because it was Jupiter (originally Zeus) who turned seven Pleiades into stars (or so the myth goes )

That might be, but Zeus created about half the constellations and stars that way. Whenever he needed to reward someone or save one of his flings - *poof* - new constellation. I don't know why there would be a special link with the Pleiades. My gut feeling is that something along the lines of Marco's suggestion is more likely. Ruler of the heavens.