Eh... I'm not personally a fan of Persephone being used as a first name. It isn't terrible, though - just a bit odd, a little pretentious, and much too delicate for my taste. I like Percy as a nickname.As for the sibset you mentioned... if it were simply Thalia and Jason, bold obviousness relating to mythology would not be immediately what I thought. I would eventually, in my mind, acknowledge Thalia's connections, though would not focus on it. Jason, however, is not a name that I would tie to Greek mythology... unless I was aware of the parents' interest, or if they were themselves Greek, it probably wouldn't occur to me. In fact, I think it looks out of place when placed next to Persephone and Thalia.