I did know, since liraen had kindly offered to do it. :)

Germaine was Charles' stepgrandmother (second wife to Ferdinand of Aragon) whom he had his presumably first affair with when he was 17 and she was just a decade older and they were both outsiders in Castile. As I mentioned, Charles, who'd grown up in Flanders (with French as his first language, btw), was by no means greeted with open arms, when arriving in the Spanish countries he'd inherited; au contraire, he was massively resented, and people thought if it had to be one of the Habsburg grandkids, it should be younger brother Ferdinand who after all had been raised in Spain. And Germaine had been Not Isabella for everyone as soon as she arrived, resented as a French outsider. (If the woman whose widower you marry was the most famous and praised woman of Europe...) And the one child she'd given birth to had died the same day. So you can see why they'd be drawn to each other. (Due to Salon's main theme, it does amuse me that the guy she ended up marrying after her affair with Charles ended was the Margrave of Brandenburg.)