Is it possible to get german measles more than once?

No: There is only one serotype of rubella so one can only get it once if not immunized.

No: However, a kid may have been labeled German measles with a copycat virus and had it later for real.Many years ago this was never tested, and many mothers or grandmothers were confident using the label. Docs did not want them anywhere near their office to be checked. Today any suspected case is more likely to have confirmatory lab tests.