They do not. Gardevoir only breed with members of the amorphous egg group, not only because the amorphous egg group consists of the only pokémon that can produce a viable egg with the ralts line anyway but also because of the Oedipus complex concept Lanette was describing (with the most unfortunate terminology possible).
Bill, if we’re going to criticize each other’s unfortunate wording, I have a few dozen pokédex entries to talk about with you… —LH
The Pokédex According to Bill 