«Many of these systems may have formed
similarly to Kepler - 223, but then later became destabilized, perhaps by a more
distant massive
planet or perhaps by the cumulative effect of the scattering of many smaller planetesimals left over from the
planet - building process.»
The Earth - Moon doesn't orbit the Earth - Moon - Sun barycenter exactly but it is not orbiting the barycenter of the solar sysem either; to some approximation the innermost
planets and the sun must wobble around the barycenter together as they are
similarly affected by the outermost
planets which happen to be more massive as well as more
distant and thus dominate in their effects on the barycenter — things should tend to get more complicated when the
planets involved are at more similar distances.