As Olga would be the hereditary ruler, she would have to take precedence, I would imagine. Therefore, there would have to be a differentiation between her title and that of her husband. I don't know what that title would be, though. Perhaps a Grand Duke.
Or, perhaps a new title would have been created, in the same way the title of Prince Consort was created for Albert, and Duke of Edinburgh for Prince Philip.
Rachel
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