I'm a native U.S. English speaker, and while I agree you wouldn't hear this specific phrase often, this kind of construction is common when you're distinguishing between members of a certain group. E.g. if somebody says," Are all of these men cousins?" you might answer, "No, the ones at the table are brothers." In those cases you wouldn't repeat the referent as you did in your example.
cel de la masă este fratele meu = the one at the table is my brother
cea de la masă este sora mea = the one at the table is my sister
cei de la masă sunt frații mei = the ones at the table are my brothers
cele de la masă sunt surorile mele = the ones at the table are my sisters