Frankie and Ariana Grande. Bruce Glikas/Getty Images Ariana Grande’s new beau, Ethan Slater, has her brother Frankie’s stamp of approval. “I love him. He’s a very sweet guy,” Frankie said of Ariana’s boyfriend and Wicked costar in an interview with TooFab published on Wednesday, June 5. In fact, Frankie, 41, has been familiar with Slater…
