Between cheering his kid sister from the sidelines and interviewing contestants as Entertainment Tonight’s special correspondent, Donny Osmond has been spending an awful lot of time on the Dancing with the Stars stage. And with sister Marie now claiming a spot on next week’s finals, it should come as little surprise that Donny himself is considering signing up for the competition’s sixth go-round, which kicks off next March. “They’ve talked to him about it,” said a jubilant — and 30 pounds lighter — Marie following her semifinals victory Tuesday night. “He keeps going back and forth. But he could so do it. He’s danced way more than I have, and he’d be so fun, too.”