I believe that the keepers, the weird insect like creatures taking care of the citadel are indoctrinated Rachni like the ravagers. Same body structure just reaperified. They could have been around longer than we thought.
I am afraud no they are not.
The Protheans fought prime rachni aswell, so the Rachni as a Species can't be that old.
Vigil on Ilos on the other hand tells you that the keepers ate nearly as old as the Citadel itself, maybe one of the first species to be harvested.
Not the first, cause we know Harbinger is made from someone else.
Most species we know are bipedal humanoid....., with only 1% of the milky way explored, who knows how many different forms of intelligent life with multiple legs ate out there.
But no, Keepers are not related to Rachni.
If at all, they are related like Yahg are to Quarian.
The Yahg are related to the Quarians?
What do you think?