It was a common occurrence, humans warring over the ability to rule a country. There were so many in these times who could stake a claim at one or two thrones, after all.
Spain would not have minded sharing a ruler with France, as was obvious in the way he so boldly fought alongside his people, against the many other European nations who opposed the unification.
When all was said and done, however, the war was lost. Spain watched as his dear Romano was torn away from him, returned to Austria's house, and he'd never regretted a war so much.