Germany - Passport & Nationality - German Citizenship by Marriage
A woman who married a German man before 31 March 1953 became a German citizen automatically. However, the law was not gender equal and a man did not become German by marrying a German woman.
Germany is a member of the European Union. As a result, a German passport holder can live and work in any of the EU member states (including Ireland). There are some restrictions to Dual Nationality, but these apply on a case-by-case basis dependent on your circumstances.