Noriaki Sugiyama, Michiko Neya, Atsushi Miyauchi and Kenjiro Tsuda voice Vinsmoke siblings
Coming up after this weekend's One Piece episode 782, "Fist of the Devil - Showdown! Luffy vs. Grant," the anime launches into the Whole Cake Island Arc with April 9th's "Sanji Return Home - To Big Mom's Territory!" An early look at next week's issue of Jump has offered a preview of the storyline's visual and the casting for the Vinsmoke siblings.
Ichiji = Noriaki Sugiyama (Naruto's Sasuke Uchiha, Fate/stray night's Shirō Emiya)
Reiju = Michiko Neya (Fullmetal Alchemist's Riza Hawkeye, Full Metal Panic's Melissa Mao, Gunsmith Cats' Rally Vincent)
Niji = Atsushi Miyauchi
Yonji = Kenjiro Tsuda