"A grandmother? Perish the though." Eli had hair that curled around his ears too, and he was eight years Thrawn's junior. "You are far too young."

Thrawn wasn't always the best at judging how old people were, and while Astarion clearly wasn't someone barely out of being a mid-ager, he certainly wasn't old enough to be someone's grandparent. Thrawn just assumed that white hair was just a natural hair color for elves.

"You also have rather nice hands."