The Kett are actually the Collectors and the Protheans

Eh, I wouldn't agree with that just because they have some physical similarities. By that reasoning humans and asari could be related. The kett also have only two eyes and i don't see why they would evolve to lose a set. There's also nothing to suggest that any race from the milky way prior to the initiative went there. 

The collectors serve the Reapers, and the Reapers don't operate outside of the Milky Way, so i don't think kett are related. I do think they might originally be a Milky Way species, because their appearance and technology is similar to that of Milky Way species, which look so much alike because the Reapers guided their evolution for millions of years.

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.

Okay okay hear me out, I have not read one bit of the comics but I remember from mass effect one vigil talked about how a handful of scientists went to the citadel,  and it makes me wonder if they somehow made it to Andromeda, obviously the kett exault and reuse genes from the other species (hmm sounds familiar) but I totally agree. A lot of people don’t wanna connect Andromeda and the original trilogy, and some people just blame it on * rewriting and lazy animators, but I really do believe there are hints that connect the Milky Way and Andromeda in more than just the initiative. 

That would be one way to connect the dots. Since, according to Vigil, there were not enough scientists for a viable population, they could have used genetic engineering and became Kett. Or even a split to Kett and Jardeen.