For a while I thought I was the only one thinking something similar.
I think during the chaos of the last harvesting, some protheans managed to escape the Milky Way aaaall the way to Andromeda. After all, Javik said that because of the reaper chaos, some protheans didn't know what others in the empire were doing at the time, they cut all communications.
Also, the kett ideology resembles the Prothean so much.
"We conquered them, enslaved them"
"Those who share my purpose become allies, those who don't become casualties"
"We were one empire composed of many subjects" "What if they didn't want to?" "They weren't given a choice".
"Very early we encountered the dangers posed by machine intelligence"
The above lines sound like something a kett could say, but those are lines said by Javik in ME3. Even though Javik helped Shepard, the Prothean Empire was severe and forcefully "converted" other races to their vision, not giving them a choice, just the same way the Kett have been doing. God knows if Kett already had enslaved and converted other races, or they're currently fighting them too in other clusters, but Ryder and the others don't know that yet cause they haven't explore that far away.
It would make sense if their appereance from the original protheans changed a bit, just the same way the original protheans "evolved" to become the Collectors. The structure of the heads was similar, but due to the years of evolv and physical alteration, the collectors looked more like insects. Maybe that's why the Kett look a bit different (because of the thousand years of evolution, plus adding other Andromeda Races to their genetic material).
Protheans were against machine intelligence. Javik voices it and he even kinda scolds Tali when he learns what happened between the quarians and the geth. Now, some cells of the Kett were starting to mistrust the Archon and his views. Why? Cause he was obsessing over the remnant. The remnant not only includes glyphs, structures and unknown technology to the Angara, The initiative and the Kett, it also includes the Machines, you know, those little robots protecting the sites. Just like the Prothean empire, the Kett disapproved of the Archon due to his interest in 'machine intelligence'.
So I dunno, thinking about these little similarities make me think the first Kett are gonna be closely related to the protheans. That or all this little clues might just be an awesome coincidence.
