No. Sometimes a third cichlid of the same species added to the tank will cause the pair to team up against the "odd man out" but they will just as easily kill that fish. But until they succeed, they will squabble less between themselves.
The tetras are often used as dither fish when discus and angels do nothing but hide. Makes them feel like there is nothing to be aftraid of if little tetras are out swimming around.
But when your cichlids breed, your dither fish may be a problem in that they can very quickly dive in and eat a couple fry and dash off scott-free! A few dither fish can eat quite a lot of fry in a hurry.