Well, convergent evolution as it's called, is surprisingly common. The idea that the same thing evolved completely separately multiple times. For example, wings. Bats, birds, insects, even fish - all evolved wings separately as the solution to whatever challenge they had.

Eyes evolved several times too, camouflage and mimicry, flipper fins in dolphins (mammals) and sharks (fish) - which is why sharks are vertical and dolphins are horizontal.

It's possible that the need for a brainy nervous system was needed but the animal kingdom took over that environment faster... so I think it's possible!