A drilling system includes a drillstring and a power section further including a stator having a stator axis and a rotor within the stator. The rotor rotates eccentrically within the stator in response to fluid flowing therebetween. Additionally, the system includes a coupling section including first, second, and third rotation members having a first, second, and third axes, respectively. The third rotation member is coupled to the first and second rotation members. The third rotation member is configured to move radially relative to the first and second rotation members as the first, second, and third rotation members rotate about the first, second, and third axes, respectively. Further, the system includes an input shaft coupled to the rotor and first rotation member. The input shaft and first rotation member rotate with the rotor eccentrically to the stator axis and the second rotation member rotates concentrically about the stator axis.