A common problem that the οι can't be heard in the fast audio
What is the singular of parents? Γονός; The ending of γονείς doesn't follow the rules for masculine plural. Is this some kind of exeception?
The singular is γονέας or γονιός. It used to be γονεύς. To help you, Wiktionary is usually good at giving you accurate results even when typing a declension in the search box. :)