There is Yarishna and Karishna Ayala, but although one is clearly more muscular, I think they both lift. It's just that Yarishna competes at a pro level, while Karishna just kinda lifts to stay in shape (or maintain a certain figure).
I saw a video once where a guy interviews a girl one day and the next day she turns up looking very muscular. The muscular girl was Anne Whelan, the other girl her sister. Can't remember if they were twins.
I know I’ve seen instances before where only one twin lifts. I can’t remember the names though, anyone able to help?