Well Zenos is a special case considering who his great grandfather is. So, he's already cheating. There are some who are able to use magic. They're an interesting race as if I have my lore correct their ancestors were those who lived in the clockworks city of Galug. Back during Ramza's time. Which I want to say could use magic? Then they just happen to be chased from Corvos the area that G'raha is from. You know the people who still had Allagan royal blood being passed down.

Thancred was able to use magic and his own aether before being altered by the use of the spell Flow. He can sort of use his own aether still, but it's harder. It's why he nearly died during his fight with Ran'jit.