The recent detection of the third planet in Kepler-47 has shown that binary stars can host several planets in circumbinary orbits .
To understand the evolution of such systems we have performed two-dimensional hydrodynamic simulations of the circumbinary disc with two embedded planets for several Kepler systems .
In two cases , Kepler-47 and -413 , the planets are captured in a 1:1 mean-motion resonance at the planet parking position near the inner edge of the disc .
The orbits are fully aligned , have mean eccentricities of about 0.25 to 0.30 , and the planets are entangled in a horseshoe type of motion .
Subsequent n-body simulations without the disc show that the configurations are stable .
Our results point to the existence of a new class of stable resonant orbits around binary stars .
It remains to be seen if such orbits exist in reality .