No, external capacitors are not needed on the 32KIN and 32KOUT pins. The 32KIN and 32KOUT pins have an internal capacitance of 6pF each. Therefore, only a 32.768kHz crystal (XTAL) should be connected to these pins. The characteristics of the crystal should be CL=6pF and an maximum effective series resistance (ESR) of 70kohms.