Candidates Afforded Dignity, Equality and Training (CADET) Act of 2021 This bill requires the Departments of Defense, Homeland Security, and Transportation to prescribe regulations ensuring that the parental guardianship rights of cadets and midshipmen attending military service academies are protected consistent with individual and academic responsibilities. Cadets and midshipmen with dependents must establish a family care plan with appropriate academy leadership. Pregnant cadets and midshipmen must be provided with, at minimum, the options to (1) take leave from the military service academy for up to one year, (2) fully release from the military service academy and any related obligations, and (3) enlist in active-duty service. Males fathering a child while enrolled at a military service academy must not be required to give up parental rights and must not acquire any benefits or leave considerations as a result of fathering a child, with certain exceptions (e.g., leave to attend the birth).