The attached drawing shows a typical power seat wiring schematic.
Notice the three motors are powered to rotate forward or reverse depending on the desired function. The relays simply reverse the electrical polarity to reverse the motor.
The drawing shows a pair of relays for each motor controlled by single pole double throw center off momentary (SPDT) switch.
Switches can be used in place of the relays but need to be rated at least 15 amps and they would be double pole double throw center off momentary (DPDT).