First: Welcome to the club.
Regarding the trait: You might want to re-read page 76 of the core rules (desolée; je n’ai pas les règles en francais) where traits are defined.
In principle, players can have personal traits and are actively encouraged to make suggestions to the GM on new traits. But. I think a personal trait should be neutral and neither an advantage nor a complication. Simply, for balancing reasons. Take Geordie’s Visor. Of course, he can see a spectrum much wider than most other species (and certainly most humans), but if taken from him or damaged, he is completely blind.
Regarding the “pretty” trait, I have some reservations. I, personally, would probably not allow it, because it brings sexism in my game as a regular trope. I had this before, I did not like it very much. But this is up to you and your group. Please discuss this with your players, before you allow it.
(Besides, since you used “he/his” for your captain’s player: If he’s playing a cis-male, the appropriate trait would probably be “handsome”; some Americans once told me that “pretty” is for females and “handsome” for males. May the native speakers around correct me, please!)