The Traveller RPG has the Hivers and the K'Kree. Who didn't evolve on the same planet, but do have competing interstellar empires.

The Hivers are omnivorous giant starfish, who eat their non-sentient young as a form of population control. IIRC they can't stop themselves constantly spawning young as it does nasty things to their biochemistry.

The K'kree are centauroid herbivores and did have a competing intelligent carnivore species on their planet, until they wiped them out at about the early gunpowder stage. And then they got into space, and kept on wiping out carnivores and omnivores.

And then they run into each other.