askchapo

i have a friend who speaks two languages and when i try to teach her how to speak a third she has the accent of her secondary language not her primary one.

brains are weird

In my mind he didn't learn the new language right away due to the whole trauma of everyone he knows dying and being rescue-kidnapped, and spoke and practiced his native language for a long time because he thought he would find his sister and she might still speak it

He watches a lot of Space-Mexican TV.

Most actors are meant to be speaking galactic basic (which we translate into English or whatever the dub is in non English countries) it may be that Kernari and Basic are more similar than it appears to us and gave him an accent. He also did time in juvenile prison and in a paramilitary unit, so he might have picked it up like the person who brings a a slight accent back from studying overseas.

he was always flying around to different planets salvaging or stealing stuff to sell; maybe he primarily spoke Spacesperanto

my friends are brothers like 2 years apart who came to the US at the same time. the older one has a faint accent, the younger one has none. point being its different for everyone if and when they lose their accent, seems entirely plausible to me that his character just never did.